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	$155.61	12.573%	$175.1748	$175.17	$175.15	$175.20
Purchase #2	$105.41	12.621%	$118.7138	$118.71	$118.70	$118.70
Purchase #3	$125.33	11.662%	$139.946	$139.95	$139.95	$139.90
Purchase #4	$156.74	5.374%	$165.1632	$165.16	$165.15	$165.20
Purchase #5	$124.34	9.663%	$136.355	$136.36	$136.35	$136.40
Purchase #6	$181.34	8.237%	$196.277	$196.28	$196.30	$196.30
Purchase #7	$127.66	11.575%	$142.4366	$142.44	$142.45	$142.40
7 purchase totals =	$976.43		$1,074.0664	$1,074.07	$1,074.05	$1,074.10