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	$124.45	10.668%	$137.7263	$137.73	$137.75	$137.70
Purchase #2	$107.56	3.748%	$111.5913	$111.59	$111.60	$111.60
Purchase #3	$126.27	13.431%	$143.2293	$143.23	$143.25	$143.20
Purchase #4	$222.90	12.297%	$250.31	$250.31	$250.30	$250.30
Purchase #5	$242.43	13.315%	$274.7096	$274.71	$274.70	$274.70
Purchase #6	$101.25	5.211%	$106.5261	$106.53	$106.55	$106.50
Purchase #7	$153.51	10.515%	$169.6516	$169.65	$169.65	$169.70
7 purchase totals =	$1,078.37		$1,193.7442	$1,193.75	$1,193.80	$1,193.70