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	$111.61	10.516%	$123.3469	$123.35	$123.35	$123.30
Purchase #2	$55.33	8.851%	$60.2273	$60.23	$60.25	$60.20
Purchase #3	$53.76	11.371%	$59.873	$59.87	$59.85	$59.90
Purchase #4	$134.63	11.872%	$150.6133	$150.61	$150.60	$150.60
Purchase #5	$67.79	13.102%	$76.6718	$76.67	$76.65	$76.70
Purchase #6	$93.47	3.492%	$96.734	$96.73	$96.75	$96.70
Purchase #7	$139.61	8.713%	$151.7742	$151.77	$151.75	$151.80
7 purchase totals =	$656.20		$719.2405	$719.23	$719.20	$719.20