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	$208.64	6.733%	$222.6877	$222.69	$222.70	$222.70
Purchase #2	$120.38	5.543%	$127.0527	$127.05	$127.05	$127.10
Purchase #3	$240.74	7.769%	$259.4431	$259.44	$259.45	$259.40
Purchase #4	$199.32	11.143%	$221.5302	$221.53	$221.55	$221.50
Purchase #5	$134.89	4.819%	$141.3903	$141.39	$141.40	$141.40
Purchase #6	$49.81	8.355%	$53.9716	$53.97	$53.95	$54.00
Purchase #7	$61.34	13.814%	$69.8135	$69.81	$69.80	$69.80
7 purchase totals =	$1,015.12		$1,095.8891	$1,095.88	$1,095.90	$1,095.90