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	$141.72	4.723%	$148.4134	$148.41	$148.40	$148.40
Purchase #2	$174.98	8.356%	$189.6013	$189.60	$189.60	$189.60
Purchase #3	$205.64	13.468%	$233.3356	$233.34	$233.35	$233.30
Purchase #4	$172.52	11.192%	$191.8284	$191.83	$191.85	$191.80
Purchase #5	$244.52	7.378%	$262.5607	$262.56	$262.55	$262.60
Purchase #6	$32.97	13.747%	$37.5024	$37.50	$37.50	$37.50
Purchase #7	$148.75	13.873%	$169.3861	$169.39	$169.40	$169.40
7 purchase totals =	$1,121.10		$1,232.6279	$1,232.63	$1,232.65	$1,232.60