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	$223.57	13.265%	$253.2266	$253.23	$253.25	$253.20
Purchase #2	$100.84	10.517%	$111.4453	$111.45	$111.45	$111.40
Purchase #3	$64.81	7.838%	$69.8898	$69.89	$69.90	$69.90
Purchase #4	$100.86	12.191%	$113.1558	$113.16	$113.15	$113.20
Purchase #5	$41.90	8.252%	$45.3576	$45.36	$45.35	$45.40
Purchase #6	$206.40	7.626%	$222.1401	$222.14	$222.15	$222.10
Purchase #7	$191.26	13.206%	$216.5178	$216.52	$216.50	$216.50
7 purchase totals =	$929.64		$1,031.7330	$1,031.75	$1,031.75	$1,031.70