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	$41.67	10.581%	$46.0791	$46.08	$46.10	$46.10
Purchase #2	$45.88	9.111%	$50.0601	$50.06	$50.05	$50.10
Purchase #3	$153.72	5.784%	$162.6112	$162.61	$162.60	$162.60
Purchase #4	$93.82	7.266%	$100.637	$100.64	$100.65	$100.60
Purchase #5	$89.68	5.589%	$94.6922	$94.69	$94.70	$94.70
Purchase #6	$223.59	9.819%	$245.5443	$245.54	$245.55	$245.50
Purchase #7	$231.72	5.168%	$243.6953	$243.70	$243.70	$243.70
7 purchase totals =	$880.08		$943.3192	$943.32	$943.35	$943.30