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	$40.60	12.141%	$45.5292	$45.53	$45.55	$45.50
Purchase #2	$211.29	6.763%	$225.5795	$225.58	$225.60	$225.60
Purchase #3	$118.91	11.284%	$132.3278	$132.33	$132.35	$132.30
Purchase #4	$209.69	11.640%	$234.0979	$234.10	$234.10	$234.10
Purchase #5	$168.71	6.815%	$180.2076	$180.21	$180.20	$180.20
Purchase #6	$160.77	7.513%	$172.8487	$172.85	$172.85	$172.80
Purchase #7	$68.50	3.214%	$70.7016	$70.70	$70.70	$70.70
7 purchase totals =	$978.47		$1,061.2923	$1,061.30	$1,061.35	$1,061.20