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	$166.32	3.753%	$172.562	$172.56	$172.55	$172.60
Purchase #2	$22.62	7.187%	$24.2457	$24.25	$24.25	$24.20
Purchase #3	$50.29	8.554%	$54.5918	$54.59	$54.60	$54.60
Purchase #4	$169.78	6.764%	$181.2639	$181.26	$181.25	$181.30
Purchase #5	$202.30	7.388%	$217.2459	$217.25	$217.25	$217.20
Purchase #6	$32.82	12.187%	$36.8198	$36.82	$36.80	$36.80
Purchase #7	$131.59	13.691%	$149.606	$149.61	$149.60	$149.60
7 purchase totals =	$775.72		$836.3351	$836.34	$836.30	$836.30