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	$182.71	5.340%	$192.4667	$192.47	$192.45	$192.50
Purchase #2	$94.55	6.482%	$100.6787	$100.68	$100.70	$100.70
Purchase #3	$136.26	3.700%	$141.3016	$141.30	$141.30	$141.30
Purchase #4	$55.56	8.808%	$60.4537	$60.45	$60.45	$60.50
Purchase #5	$93.76	10.174%	$103.2991	$103.30	$103.30	$103.30
Purchase #6	$143.39	4.493%	$149.8325	$149.83	$149.85	$149.80
Purchase #7	$48.53	10.732%	$53.7382	$53.74	$53.75	$53.70
7 purchase totals =	$754.76		$801.7705	$801.77	$801.80	$801.80