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	$175.43	12.198%	$196.829	$196.83	$196.85	$196.80
Purchase #2	$130.70	4.751%	$136.9096	$136.91	$136.90	$136.90
Purchase #3	$141.92	12.123%	$159.125	$159.13	$159.15	$159.10
Purchase #4	$42.74	5.445%	$45.0672	$45.07	$45.05	$45.10
Purchase #5	$129.32	7.575%	$139.116	$139.12	$139.10	$139.10
Purchase #6	$143.54	8.267%	$155.4065	$155.41	$155.40	$155.40
Purchase #7	$64.77	3.632%	$67.1224	$67.12	$67.10	$67.10
7 purchase totals =	$828.42		$899.5757	$899.59	$899.55	$899.50