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	$131.59	4.511%	$137.526	$137.53	$137.55	$137.50
Purchase #2	$123.92	10.719%	$137.203	$137.20	$137.20	$137.20
Purchase #3	$230.95	4.708%	$241.8231	$241.82	$241.80	$241.80
Purchase #4	$127.28	11.784%	$142.2787	$142.28	$142.30	$142.30
Purchase #5	$197.64	12.810%	$222.9577	$222.96	$222.95	$223.00
Purchase #6	$39.40	5.516%	$41.5733	$41.57	$41.55	$41.60
Purchase #7	$47.38	11.640%	$52.895	$52.90	$52.90	$52.90
7 purchase totals =	$898.16		$976.2568	$976.26	$976.25	$976.30