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	$189.55	3.520%	$196.2222	$196.22	$196.20	$196.20
Purchase #2	$28.30	4.507%	$29.5755	$29.58	$29.60	$29.60
Purchase #3	$53.73	10.112%	$59.1632	$59.16	$59.15	$59.20
Purchase #4	$113.26	10.584%	$125.2474	$125.25	$125.25	$125.20
Purchase #5	$244.52	12.704%	$275.5838	$275.58	$275.60	$275.60
Purchase #6	$44.34	3.871%	$46.0564	$46.06	$46.05	$46.10
Purchase #7	$138.61	7.822%	$149.4521	$149.45	$149.45	$149.50
7 purchase totals =	$812.31		$881.3006	$881.30	$881.30	$881.40