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	$46.97	7.590%	$50.535	$50.54	$50.55	$50.50
Purchase #2	$83.25	7.707%	$89.6661	$89.67	$89.65	$89.70
Purchase #3	$243.78	3.555%	$252.4464	$252.45	$252.45	$252.40
Purchase #4	$231.55	9.326%	$253.1444	$253.14	$253.15	$253.10
Purchase #5	$221.95	5.784%	$234.7876	$234.79	$234.80	$234.80
Purchase #6	$238.43	7.419%	$256.1191	$256.12	$256.10	$256.10
Purchase #7	$111.40	11.187%	$123.8623	$123.86	$123.85	$123.90
7 purchase totals =	$1,177.33		$1,260.5609	$1,260.57	$1,260.55	$1,260.50