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	$88.35	9.103%	$96.3925	$96.39	$96.40	$96.40
Purchase #2	$48.45	5.103%	$50.9224	$50.92	$50.90	$50.90
Purchase #3	$213.79	13.634%	$242.9381	$242.94	$242.95	$242.90
Purchase #4	$247.50	4.284%	$258.1029	$258.10	$258.10	$258.10
Purchase #5	$115.29	13.717%	$131.1043	$131.10	$131.10	$131.10
Purchase #6	$18.38	13.535%	$20.8677	$20.87	$20.85	$20.90
Purchase #7	$131.53	10.252%	$145.0145	$145.01	$145.00	$145.00
7 purchase totals =	$863.29		$945.3424	$945.33	$945.30	$945.30