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	$154.55	8.163%	$167.1659	$167.17	$167.15	$167.20
Purchase #2	$222.83	4.829%	$233.5905	$233.59	$233.60	$233.60
Purchase #3	$222.65	9.516%	$243.8374	$243.84	$243.85	$243.80
Purchase #4	$6.93	10.830%	$7.6805	$7.68	$7.70	$7.70
Purchase #5	$153.55	13.806%	$174.7491	$174.75	$174.75	$174.70
Purchase #6	$108.74	12.807%	$122.6663	$122.67	$122.65	$122.70
Purchase #7	$59.48	11.740%	$66.463	$66.46	$66.45	$66.50
7 purchase totals =	$928.73		$1,016.1527	$1,016.16	$1,016.15	$1,016.20