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	$196.47	13.350%	$222.6987	$222.70	$222.70	$222.70
Purchase #2	$237.46	11.407%	$264.5471	$264.55	$264.55	$264.50
Purchase #3	$219.35	13.744%	$249.4975	$249.50	$249.50	$249.50
Purchase #4	$157.70	9.171%	$172.1627	$172.16	$172.15	$172.20
Purchase #5	$154.46	7.698%	$166.3503	$166.35	$166.35	$166.40
Purchase #6	$233.79	8.506%	$253.6762	$253.68	$253.70	$253.70
Purchase #7	$125.51	13.570%	$142.5417	$142.54	$142.55	$142.50
7 purchase totals =	$1,324.74		$1,471.4742	$1,471.48	$1,471.50	$1,471.50