Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$86.81	3.113%	$89.5124	$89.51	$89.50	$89.50
Purchase #2	$223.98	8.477%	$242.9668	$242.97	$242.95	$243.00
Purchase #3	$79.56	3.465%	$82.3168	$82.32	$82.30	$82.30
Purchase #4	$241.52	13.515%	$274.1614	$274.16	$274.15	$274.20
Purchase #5	$198.65	11.784%	$222.0589	$222.06	$222.05	$222.10
Purchase #6	$170.35	8.806%	$185.351	$185.35	$185.35	$185.40
Purchase #7	$85.60	11.541%	$95.4791	$95.48	$95.50	$95.50
7 purchase totals =	$1,086.47		$1,191.8464	$1,191.85	$1,191.80	$1,192.00