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	$228.25	10.155%	$251.4288	$251.43	$251.45	$251.40
Purchase #2	$206.38	10.437%	$227.9199	$227.92	$227.90	$227.90
Purchase #3	$210.89	10.802%	$233.6703	$233.67	$233.65	$233.70
Purchase #4	$191.47	9.425%	$209.516	$209.52	$209.50	$209.50
Purchase #5	$244.75	11.375%	$272.5903	$272.59	$272.60	$272.60
Purchase #6	$141.40	9.604%	$154.9801	$154.98	$155.00	$155.00
Purchase #7	$102.89	13.439%	$116.7174	$116.72	$116.70	$116.70
7 purchase totals =	$1,326.03		$1,466.8228	$1,466.83	$1,466.80	$1,466.80