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	$190.37	12.243%	$213.677	$213.68	$213.70	$213.70
Purchase #2	$31.58	4.501%	$33.0014	$33.00	$33.00	$33.00
Purchase #3	$214.64	10.108%	$236.3358	$236.34	$236.35	$236.30
Purchase #4	$69.92	11.339%	$77.8482	$77.85	$77.85	$77.80
Purchase #5	$207.89	10.573%	$229.8702	$229.87	$229.85	$229.90
Purchase #6	$78.35	12.714%	$88.3114	$88.31	$88.30	$88.30
Purchase #7	$54.27	9.684%	$59.5255	$59.53	$59.55	$59.50
7 purchase totals =	$847.02		$938.5695	$938.58	$938.60	$938.50