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	$70.66	6.297%	$75.1095	$75.11	$75.10	$75.10
Purchase #2	$136.73	13.580%	$155.2979	$155.30	$155.30	$155.30
Purchase #3	$134.32	7.581%	$144.5028	$144.50	$144.50	$144.50
Purchase #4	$182.49	7.587%	$196.3355	$196.34	$196.35	$196.30
Purchase #5	$8.32	7.126%	$8.9129	$8.91	$8.90	$8.90
Purchase #6	$133.74	9.152%	$145.9799	$145.98	$146.00	$146.00
Purchase #7	$39.51	7.575%	$42.5029	$42.50	$42.50	$42.50
7 purchase totals =	$705.77		$768.6414	$768.64	$768.65	$768.60