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	$166.81	10.629%	$184.5402	$184.54	$184.55	$184.50
Purchase #2	$84.59	12.127%	$94.8482	$94.85	$94.85	$94.80
Purchase #3	$63.88	11.362%	$71.138	$71.14	$71.15	$71.10
Purchase #4	$20.80	8.141%	$22.4933	$22.49	$22.50	$22.50
Purchase #5	$244.78	7.129%	$262.2304	$262.23	$262.25	$262.20
Purchase #6	$146.95	12.764%	$165.7067	$165.71	$165.70	$165.70
Purchase #7	$89.67	11.775%	$100.2286	$100.23	$100.25	$100.20
7 purchase totals =	$817.48		$901.1854	$901.19	$901.25	$901.00