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	$50.51	9.197%	$55.1554	$55.16	$55.15	$55.20
Purchase #2	$122.89	12.198%	$137.8801	$137.88	$137.90	$137.90
Purchase #3	$241.79	9.450%	$264.6392	$264.64	$264.65	$264.60
Purchase #4	$45.82	7.749%	$49.3706	$49.37	$49.35	$49.40
Purchase #5	$180.38	4.143%	$187.8531	$187.85	$187.85	$187.90
Purchase #6	$217.47	3.440%	$224.951	$224.95	$224.95	$225.00
Purchase #7	$131.75	11.230%	$146.5455	$146.55	$146.55	$146.50
7 purchase totals =	$990.61		$1,066.3949	$1,066.40	$1,066.40	$1,066.50