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	$133.67	4.521%	$139.7132	$139.71	$139.70	$139.70
Purchase #2	$241.88	13.171%	$273.738	$273.74	$273.75	$273.70
Purchase #3	$168.42	13.753%	$191.5828	$191.58	$191.60	$191.60
Purchase #4	$216.56	12.747%	$244.1649	$244.16	$244.15	$244.20
Purchase #5	$178.33	4.185%	$185.7931	$185.79	$185.80	$185.80
Purchase #6	$124.47	13.220%	$140.9249	$140.92	$140.90	$140.90
Purchase #7	$146.54	4.329%	$152.8837	$152.88	$152.90	$152.90
7 purchase totals =	$1,209.87		$1,328.8006	$1,328.78	$1,328.80	$1,328.80