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	$5.29	8.180%	$5.7227	$5.72	$5.70	$5.70
Purchase #2	$75.34	4.172%	$78.4832	$78.48	$78.50	$78.50
Purchase #3	$115.77	13.127%	$130.9671	$130.97	$130.95	$131.00
Purchase #4	$159.43	4.484%	$166.5788	$166.58	$166.60	$166.60
Purchase #5	$51.45	3.523%	$53.2626	$53.26	$53.25	$53.30
Purchase #6	$56.78	12.624%	$63.9479	$63.95	$63.95	$63.90
Purchase #7	$190.89	11.620%	$213.0714	$213.07	$213.05	$213.10
7 purchase totals =	$654.95		$712.0337	$712.03	$712.00	$712.10