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	$119.77	4.315%	$124.9381	$124.94	$124.95	$124.90
Purchase #2	$99.94	5.624%	$105.5606	$105.56	$105.55	$105.60
Purchase #3	$226.45	12.737%	$255.2929	$255.29	$255.30	$255.30
Purchase #4	$234.65	8.451%	$254.4803	$254.48	$254.50	$254.50
Purchase #5	$179.97	4.632%	$188.3062	$188.31	$188.30	$188.30
Purchase #6	$72.43	12.537%	$81.5105	$81.51	$81.50	$81.50
Purchase #7	$214.54	9.639%	$235.2195	$235.22	$235.20	$235.20
7 purchase totals =	$1,147.75		$1,245.3081	$1,245.31	$1,245.30	$1,245.30