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	$247.27	10.871%	$274.1507	$274.15	$274.15	$274.20
Purchase #2	$66.89	13.203%	$75.7215	$75.72	$75.70	$75.70
Purchase #3	$188.79	4.166%	$196.655	$196.66	$196.65	$196.70
Purchase #4	$132.96	10.328%	$146.6921	$146.69	$146.70	$146.70
Purchase #5	$177.52	11.188%	$197.3809	$197.38	$197.40	$197.40
Purchase #6	$43.76	7.172%	$46.8985	$46.90	$46.90	$46.90
Purchase #7	$78.71	13.364%	$89.2288	$89.23	$89.25	$89.20
7 purchase totals =	$935.90		$1,026.7275	$1,026.73	$1,026.75	$1,026.80