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	$71.75	6.699%	$76.5565	$76.56	$76.55	$76.60
Purchase #2	$25.38	12.603%	$28.5786	$28.58	$28.60	$28.60
Purchase #3	$146.75	3.325%	$151.6294	$151.63	$151.65	$151.60
Purchase #4	$59.47	10.407%	$65.659	$65.66	$65.65	$65.70
Purchase #5	$54.90	11.550%	$61.241	$61.24	$61.25	$61.20
Purchase #6	$168.81	13.333%	$191.3174	$191.32	$191.30	$191.30
Purchase #7	$139.32	9.426%	$152.4523	$152.45	$152.45	$152.50
7 purchase totals =	$666.38		$727.4342	$727.44	$727.45	$727.50