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	$49.71	5.344%	$52.3665	$52.37	$52.35	$52.40
Purchase #2	$130.43	6.846%	$139.3592	$139.36	$139.35	$139.40
Purchase #3	$37.80	13.349%	$42.8459	$42.85	$42.85	$42.80
Purchase #4	$176.60	8.243%	$191.1571	$191.16	$191.15	$191.20
Purchase #5	$48.63	11.576%	$54.2594	$54.26	$54.25	$54.30
Purchase #6	$143.51	3.829%	$149.005	$149.01	$149.00	$149.00
Purchase #7	$145.71	4.725%	$152.5948	$152.59	$152.60	$152.60
7 purchase totals =	$732.39		$781.5879	$781.60	$781.55	$781.70