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	$248.80	8.172%	$269.1319	$269.13	$269.15	$269.10
Purchase #2	$7.45	3.499%	$7.7107	$7.71	$7.70	$7.70
Purchase #3	$198.76	12.119%	$222.8477	$222.85	$222.85	$222.80
Purchase #4	$200.50	10.486%	$221.5244	$221.52	$221.50	$221.50
Purchase #5	$34.89	10.103%	$38.4149	$38.41	$38.40	$38.40
Purchase #6	$56.65	12.775%	$63.887	$63.89	$63.90	$63.90
Purchase #7	$76.77	6.388%	$81.6741	$81.67	$81.65	$81.70
7 purchase totals =	$823.82		$905.1907	$905.18	$905.15	$905.10