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	$191.29	10.679%	$211.7179	$211.72	$211.70	$211.70
Purchase #2	$172.85	5.360%	$182.1148	$182.11	$182.10	$182.10
Purchase #3	$110.50	9.237%	$120.7069	$120.71	$120.70	$120.70
Purchase #4	$102.74	13.186%	$116.2873	$116.29	$116.30	$116.30
Purchase #5	$49.32	8.159%	$53.344	$53.34	$53.35	$53.30
Purchase #6	$82.84	11.624%	$92.4693	$92.47	$92.45	$92.50
Purchase #7	$90.38	11.222%	$100.5224	$100.52	$100.50	$100.50
7 purchase totals =	$799.92		$877.1626	$877.16	$877.10	$877.10