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	$238.26	8.467%	$258.4335	$258.43	$258.45	$258.40
Purchase #2	$162.69	13.206%	$184.1748	$184.17	$184.15	$184.20
Purchase #3	$212.45	13.119%	$240.3213	$240.32	$240.30	$240.30
Purchase #4	$11.66	5.476%	$12.2985	$12.30	$12.30	$12.30
Purchase #5	$94.72	10.282%	$104.4591	$104.46	$104.45	$104.50
Purchase #6	$30.65	11.788%	$34.263	$34.26	$34.25	$34.30
Purchase #7	$57.67	6.419%	$61.3718	$61.37	$61.35	$61.40
7 purchase totals =	$808.10		$895.3220	$895.31	$895.25	$895.40