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	$76.99	8.745%	$83.7228	$83.72	$83.70	$83.70
Purchase #2	$194.96	7.801%	$210.1688	$210.17	$210.15	$210.20
Purchase #3	$105.46	6.130%	$111.9247	$111.92	$111.90	$111.90
Purchase #4	$218.78	5.739%	$231.3358	$231.34	$231.35	$231.30
Purchase #5	$178.83	13.585%	$203.1241	$203.12	$203.10	$203.10
Purchase #6	$204.81	12.107%	$229.6063	$229.61	$229.60	$229.60
Purchase #7	$22.99	6.511%	$24.4869	$24.49	$24.50	$24.50
7 purchase totals =	$1,002.82		$1,094.3694	$1,094.37	$1,094.30	$1,094.30