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	$69.50	3.128%	$71.674	$71.67	$71.65	$71.70
Purchase #2	$101.60	6.422%	$108.1248	$108.12	$108.10	$108.10
Purchase #3	$67.59	5.204%	$71.1074	$71.11	$71.10	$71.10
Purchase #4	$35.76	4.481%	$37.3624	$37.36	$37.35	$37.40
Purchase #5	$98.80	10.300%	$108.9764	$108.98	$109.00	$109.00
Purchase #6	$14.41	6.519%	$15.3494	$15.35	$15.35	$15.30
Purchase #7	$71.96	10.593%	$79.5827	$79.58	$79.60	$79.60
7 purchase totals =	$459.62		$492.1771	$492.17	$492.15	$492.20