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	$176.64	8.362%	$191.4106	$191.41	$191.40	$191.40
Purchase #2	$64.53	11.399%	$71.8858	$71.89	$71.90	$71.90
Purchase #3	$60.90	13.123%	$68.8919	$68.89	$68.90	$68.90
Purchase #4	$209.45	6.380%	$222.8129	$222.81	$222.80	$222.80
Purchase #5	$194.74	10.345%	$214.8859	$214.89	$214.90	$214.90
Purchase #6	$50.48	11.707%	$56.3897	$56.39	$56.40	$56.40
Purchase #7	$236.96	10.579%	$262.028	$262.03	$262.05	$262.00
7 purchase totals =	$993.70		$1,088.3048	$1,088.31	$1,088.35	$1,088.30