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	$204.60	4.167%	$213.1257	$213.13	$213.15	$213.10
Purchase #2	$131.33	6.475%	$139.8336	$139.83	$139.85	$139.80
Purchase #3	$196.47	7.449%	$211.1051	$211.11	$211.10	$211.10
Purchase #4	$40.75	11.442%	$45.4126	$45.41	$45.40	$45.40
Purchase #5	$236.42	13.321%	$267.9135	$267.91	$267.90	$267.90
Purchase #6	$197.99	12.607%	$222.9506	$222.95	$222.95	$223.00
Purchase #7	$152.96	10.684%	$169.3022	$169.30	$169.30	$169.30
7 purchase totals =	$1,160.52		$1,269.6433	$1,269.64	$1,269.65	$1,269.60