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	$109.33	3.489%	$113.1445	$113.14	$113.15	$113.10
Purchase #2	$118.55	10.673%	$131.2028	$131.20	$131.20	$131.20
Purchase #3	$89.39	13.336%	$101.3111	$101.31	$101.30	$101.30
Purchase #4	$19.69	11.422%	$21.939	$21.94	$21.95	$21.90
Purchase #5	$71.51	4.672%	$74.8509	$74.85	$74.85	$74.90
Purchase #6	$129.56	10.822%	$143.581	$143.58	$143.60	$143.60
Purchase #7	$148.57	6.391%	$158.0651	$158.07	$158.05	$158.10
7 purchase totals =	$686.60		$744.0944	$744.09	$744.10	$744.10