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	$240.51	6.362%	$255.8112	$255.81	$255.80	$255.80
Purchase #2	$165.83	5.140%	$174.3537	$174.35	$174.35	$174.40
Purchase #3	$82.74	10.358%	$91.3102	$91.31	$91.30	$91.30
Purchase #4	$127.72	3.247%	$131.8671	$131.87	$131.85	$131.90
Purchase #5	$111.88	13.456%	$126.9346	$126.93	$126.95	$126.90
Purchase #6	$214.34	10.536%	$236.9229	$236.92	$236.90	$236.90
Purchase #7	$218.62	13.678%	$248.5228	$248.52	$248.50	$248.50
7 purchase totals =	$1,161.64		$1,265.7225	$1,265.71	$1,265.65	$1,265.70