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	$188.95	3.788%	$196.1074	$196.11	$196.10	$196.10
Purchase #2	$238.41	3.838%	$247.5602	$247.56	$247.55	$247.60
Purchase #3	$19.33	7.186%	$20.7191	$20.72	$20.70	$20.70
Purchase #4	$35.42	13.350%	$40.1486	$40.15	$40.15	$40.10
Purchase #5	$148.76	11.106%	$165.2813	$165.28	$165.30	$165.30
Purchase #6	$137.88	7.625%	$148.3934	$148.39	$148.40	$148.40
Purchase #7	$88.68	8.130%	$95.8897	$95.89	$95.90	$95.90
7 purchase totals =	$857.43		$914.0997	$914.10	$914.10	$914.10