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	$103.53	9.325%	$113.1842	$113.18	$113.20	$113.20
Purchase #2	$63.95	5.580%	$67.5184	$67.52	$67.50	$67.50
Purchase #3	$44.51	5.851%	$47.1143	$47.11	$47.10	$47.10
Purchase #4	$69.95	4.449%	$73.0621	$73.06	$73.05	$73.10
Purchase #5	$124.38	6.182%	$132.0692	$132.07	$132.05	$132.10
Purchase #6	$244.45	12.563%	$275.1603	$275.16	$275.15	$275.20
Purchase #7	$119.43	6.661%	$127.3852	$127.39	$127.40	$127.40
7 purchase totals =	$770.20		$835.4937	$835.49	$835.45	$835.60