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	$118.77	10.680%	$131.4546	$131.45	$131.45	$131.50
Purchase #2	$114.57	9.227%	$125.1414	$125.14	$125.15	$125.10
Purchase #3	$63.37	3.335%	$65.4834	$65.48	$65.50	$65.50
Purchase #4	$127.72	4.222%	$133.1123	$133.11	$133.10	$133.10
Purchase #5	$25.67	9.331%	$28.0653	$28.07	$28.05	$28.10
Purchase #6	$199.39	11.799%	$222.916	$222.92	$222.90	$222.90
Purchase #7	$41.69	5.223%	$43.8675	$43.87	$43.85	$43.90
7 purchase totals =	$691.18		$750.0405	$750.04	$750.00	$750.10