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	$110.43	6.231%	$117.3109	$117.31	$117.30	$117.30
Purchase #2	$83.58	7.282%	$89.6663	$89.67	$89.65	$89.70
Purchase #3	$85.58	8.386%	$92.7567	$92.76	$92.75	$92.80
Purchase #4	$153.59	7.839%	$165.6299	$165.63	$165.65	$165.60
Purchase #5	$189.50	10.718%	$209.8106	$209.81	$209.80	$209.80
Purchase #6	$165.58	4.183%	$172.5062	$172.51	$172.50	$172.50
Purchase #7	$193.56	7.377%	$207.8389	$207.84	$207.85	$207.80
7 purchase totals =	$981.82		$1,055.5195	$1,055.53	$1,055.50	$1,055.50