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	$248.48	9.332%	$271.6682	$271.67	$271.65	$271.70
Purchase #2	$46.31	10.341%	$51.0989	$51.10	$51.10	$51.10
Purchase #3	$235.53	11.496%	$262.6065	$262.61	$262.60	$262.60
Purchase #4	$164.45	10.704%	$182.0527	$182.05	$182.05	$182.10
Purchase #5	$116.91	11.211%	$130.0168	$130.02	$130.00	$130.00
Purchase #6	$64.35	3.258%	$66.4465	$66.45	$66.45	$66.40
Purchase #7	$168.75	12.240%	$189.405	$189.41	$189.40	$189.40
7 purchase totals =	$1,044.78		$1,153.2946	$1,153.31	$1,153.25	$1,153.30