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	$128.79	11.132%	$143.1269	$143.13	$143.15	$143.10
Purchase #2	$206.62	7.807%	$222.7508	$222.75	$222.75	$222.80
Purchase #3	$95.98	5.802%	$101.5488	$101.55	$101.55	$101.50
Purchase #4	$41.90	9.554%	$45.9031	$45.90	$45.90	$45.90
Purchase #5	$161.82	6.594%	$172.4904	$172.49	$172.50	$172.50
Purchase #6	$218.32	13.502%	$247.7976	$247.80	$247.80	$247.80
Purchase #7	$144.80	7.411%	$155.5311	$155.53	$155.55	$155.50
7 purchase totals =	$998.23		$1,089.1487	$1,089.15	$1,089.20	$1,089.10