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	$187.94	5.625%	$198.5116	$198.51	$198.50	$198.50
Purchase #2	$39.32	10.717%	$43.5339	$43.53	$43.55	$43.50
Purchase #3	$157.50	9.621%	$172.6531	$172.65	$172.65	$172.70
Purchase #4	$11.51	11.340%	$12.8152	$12.82	$12.80	$12.80
Purchase #5	$239.87	10.190%	$264.3128	$264.31	$264.30	$264.30
Purchase #6	$49.42	6.827%	$52.7939	$52.79	$52.80	$52.80
Purchase #7	$135.66	7.778%	$146.2116	$146.21	$146.20	$146.20
7 purchase totals =	$821.22		$890.8321	$890.82	$890.80	$890.80