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	$209.39	12.540%	$235.6475	$235.65	$235.65	$235.60
Purchase #2	$168.37	10.323%	$185.7508	$185.75	$185.75	$185.80
Purchase #3	$137.94	13.367%	$156.3784	$156.38	$156.40	$156.40
Purchase #4	$118.64	6.671%	$126.5545	$126.55	$126.55	$126.60
Purchase #5	$37.30	8.103%	$40.3224	$40.32	$40.30	$40.30
Purchase #6	$248.57	4.109%	$258.7837	$258.78	$258.80	$258.80
Purchase #7	$61.28	9.193%	$66.9135	$66.91	$66.90	$66.90
7 purchase totals =	$981.49		$1,070.3508	$1,070.34	$1,070.35	$1,070.40