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	$217.56	7.699%	$234.3099	$234.31	$234.30	$234.30
Purchase #2	$244.56	3.241%	$252.4862	$252.49	$252.50	$252.50
Purchase #3	$102.64	8.841%	$111.7144	$111.71	$111.70	$111.70
Purchase #4	$238.38	7.507%	$256.2752	$256.28	$256.30	$256.30
Purchase #5	$42.53	11.710%	$47.5103	$47.51	$47.50	$47.50
Purchase #6	$176.39	11.440%	$196.569	$196.57	$196.55	$196.60
Purchase #7	$32.67	12.710%	$36.8224	$36.82	$36.80	$36.80
7 purchase totals =	$1,054.73		$1,135.6874	$1,135.69	$1,135.65	$1,135.70