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	$148.49	6.429%	$158.0364	$158.04	$158.05	$158.00
Purchase #2	$87.26	4.679%	$91.3429	$91.34	$91.35	$91.30
Purchase #3	$29.68	12.495%	$33.3885	$33.39	$33.40	$33.40
Purchase #4	$16.35	5.492%	$17.2479	$17.25	$17.25	$17.20
Purchase #5	$54.58	9.243%	$59.6248	$59.62	$59.60	$59.60
Purchase #6	$112.38	11.692%	$125.5195	$125.52	$125.50	$125.50
Purchase #7	$140.46	4.591%	$146.9085	$146.91	$146.90	$146.90
7 purchase totals =	$589.20		$632.0685	$632.07	$632.05	$631.90