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	$47.98	11.398%	$53.4488	$53.45	$53.45	$53.40
Purchase #2	$48.82	11.517%	$54.4426	$54.44	$54.45	$54.40
Purchase #3	$135.30	4.591%	$141.5116	$141.51	$141.50	$141.50
Purchase #4	$208.28	7.507%	$223.9156	$223.92	$223.90	$223.90
Purchase #5	$200.77	11.547%	$223.9529	$223.95	$223.95	$224.00
Purchase #6	$141.90	13.775%	$161.4467	$161.45	$161.45	$161.40
Purchase #7	$99.93	11.598%	$111.5199	$111.52	$111.50	$111.50
7 purchase totals =	$882.98		$970.2381	$970.24	$970.20	$970.10