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	$147.76	7.162%	$158.3426	$158.34	$158.35	$158.30
Purchase #2	$7.74	7.748%	$8.3397	$8.34	$8.35	$8.30
Purchase #3	$134.52	8.829%	$146.3968	$146.40	$146.40	$146.40
Purchase #4	$107.67	3.823%	$111.7862	$111.79	$111.80	$111.80
Purchase #5	$155.40	6.375%	$165.3068	$165.31	$165.30	$165.30
Purchase #6	$128.88	6.512%	$137.2727	$137.27	$137.25	$137.30
Purchase #7	$246.90	10.331%	$272.4072	$272.41	$272.40	$272.40
7 purchase totals =	$928.87		$999.8520	$999.86	$999.85	$999.80