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	$226.38	11.190%	$251.7119	$251.71	$251.70	$251.70
Purchase #2	$81.58	8.358%	$88.3985	$88.40	$88.40	$88.40
Purchase #3	$215.68	3.263%	$222.7176	$222.72	$222.70	$222.70
Purchase #4	$43.25	5.413%	$45.5911	$45.59	$45.60	$45.60
Purchase #5	$46.56	9.363%	$50.9194	$50.92	$50.90	$50.90
Purchase #6	$54.31	10.848%	$60.2015	$60.20	$60.20	$60.20
Purchase #7	$131.60	7.178%	$141.0462	$141.05	$141.05	$141.00
7 purchase totals =	$799.36		$860.5862	$860.59	$860.55	$860.50