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	$119.55	3.528%	$123.7677	$123.77	$123.75	$123.80
Purchase #2	$180.89	9.363%	$197.8267	$197.83	$197.85	$197.80
Purchase #3	$112.55	4.375%	$117.4741	$117.47	$117.45	$117.50
Purchase #4	$101.38	10.121%	$111.6407	$111.64	$111.65	$111.60
Purchase #5	$230.55	3.332%	$238.2319	$238.23	$238.25	$238.20
Purchase #6	$55.51	11.386%	$61.8304	$61.83	$61.85	$61.80
Purchase #7	$185.26	13.859%	$210.9352	$210.94	$210.95	$210.90
7 purchase totals =	$985.69		$1,061.7067	$1,061.71	$1,061.75	$1,061.60