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	$141.56	12.788%	$159.6627	$159.66	$159.65	$159.70
Purchase #2	$100.89	9.377%	$110.3505	$110.35	$110.35	$110.40
Purchase #3	$192.62	8.192%	$208.3994	$208.40	$208.40	$208.40
Purchase #4	$137.42	11.598%	$153.358	$153.36	$153.35	$153.40
Purchase #5	$203.30	4.810%	$213.0787	$213.08	$213.10	$213.10
Purchase #6	$54.85	12.605%	$61.7638	$61.76	$61.75	$61.80
Purchase #7	$99.63	10.346%	$109.9377	$109.94	$109.95	$109.90
7 purchase totals =	$930.27		$1,016.5508	$1,016.55	$1,016.55	$1,016.70