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	$157.40	9.561%	$172.449	$172.45	$172.45	$172.40
Purchase #2	$46.85	8.644%	$50.8997	$50.90	$50.90	$50.90
Purchase #3	$149.42	10.716%	$165.4318	$165.43	$165.45	$165.40
Purchase #4	$89.75	12.126%	$100.6331	$100.63	$100.65	$100.60
Purchase #5	$42.60	6.356%	$45.3077	$45.31	$45.30	$45.30
Purchase #6	$108.66	10.349%	$119.9052	$119.91	$119.90	$119.90
Purchase #7	$16.66	11.665%	$18.6034	$18.60	$18.60	$18.60
7 purchase totals =	$611.34		$673.2299	$673.23	$673.25	$673.10