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	$48.58	11.485%	$54.1594	$54.16	$54.15	$54.20
Purchase #2	$247.77	10.538%	$273.88	$273.88	$273.90	$273.90
Purchase #3	$211.80	13.387%	$240.1537	$240.15	$240.15	$240.20
Purchase #4	$222.33	7.450%	$238.8936	$238.89	$238.90	$238.90
Purchase #5	$170.78	3.145%	$176.151	$176.15	$176.15	$176.20
Purchase #6	$141.76	4.423%	$148.03	$148.03	$148.05	$148.00
Purchase #7	$131.40	7.617%	$141.4087	$141.41	$141.40	$141.40
7 purchase totals =	$1,174.42		$1,272.6764	$1,272.67	$1,272.70	$1,272.80