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	$184.57	13.409%	$209.319	$209.32	$209.30	$209.30
Purchase #2	$54.99	12.143%	$61.6674	$61.67	$61.65	$61.70
Purchase #3	$192.98	5.652%	$203.8872	$203.89	$203.90	$203.90
Purchase #4	$144.39	4.257%	$150.5367	$150.54	$150.55	$150.50
Purchase #5	$196.96	5.825%	$208.4329	$208.43	$208.45	$208.40
Purchase #6	$197.77	4.390%	$206.4521	$206.45	$206.45	$206.50
Purchase #7	$159.53	10.427%	$176.1642	$176.16	$176.15	$176.20
7 purchase totals =	$1,131.19		$1,216.4595	$1,216.46	$1,216.45	$1,216.50