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	$42.59	6.772%	$45.4742	$45.47	$45.45	$45.50
Purchase #2	$129.45	9.818%	$142.1594	$142.16	$142.15	$142.20
Purchase #3	$11.27	4.795%	$11.8104	$11.81	$11.80	$11.80
Purchase #4	$67.26	4.315%	$70.1623	$70.16	$70.15	$70.20
Purchase #5	$54.59	12.313%	$61.3117	$61.31	$61.30	$61.30
Purchase #6	$53.82	12.775%	$60.6955	$60.70	$60.70	$60.70
Purchase #7	$18.76	13.221%	$21.2403	$21.24	$21.25	$21.20
7 purchase totals =	$377.74		$412.8538	$412.85	$412.80	$412.90