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	$184.78	6.199%	$196.2345	$196.23	$196.25	$196.20
Purchase #2	$134.42	8.814%	$146.2678	$146.27	$146.25	$146.30
Purchase #3	$237.61	11.252%	$264.3459	$264.35	$264.35	$264.30
Purchase #4	$86.58	10.378%	$95.5653	$95.57	$95.55	$95.60
Purchase #5	$105.44	12.371%	$118.484	$118.48	$118.50	$118.50
Purchase #6	$191.94	11.548%	$214.1052	$214.11	$214.10	$214.10
Purchase #7	$173.30	9.673%	$190.0633	$190.06	$190.05	$190.10
7 purchase totals =	$1,114.07		$1,225.0660	$1,225.07	$1,225.05	$1,225.10