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	$188.55	4.113%	$196.3051	$196.31	$196.30	$196.30
Purchase #2	$6.63	3.320%	$6.8501	$6.85	$6.85	$6.90
Purchase #3	$76.59	11.150%	$85.1298	$85.13	$85.15	$85.10
Purchase #4	$88.58	9.537%	$97.0279	$97.03	$97.05	$97.00
Purchase #5	$230.32	5.335%	$242.6076	$242.61	$242.60	$242.60
Purchase #6	$223.69	13.117%	$253.0314	$253.03	$253.05	$253.00
Purchase #7	$103.40	12.737%	$116.5701	$116.57	$116.55	$116.60
7 purchase totals =	$917.76		$997.5220	$997.53	$997.55	$997.50