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	$145.72	12.714%	$164.2468	$164.25	$164.25	$164.20
Purchase #2	$145.84	6.476%	$155.2846	$155.28	$155.30	$155.30
Purchase #3	$59.57	11.239%	$66.2651	$66.27	$66.25	$66.30
Purchase #4	$232.57	10.311%	$256.5503	$256.55	$256.55	$256.60
Purchase #5	$101.78	4.548%	$106.409	$106.41	$106.40	$106.40
Purchase #6	$120.63	4.844%	$126.4733	$126.47	$126.45	$126.50
Purchase #7	$69.81	4.113%	$72.6813	$72.68	$72.70	$72.70
7 purchase totals =	$875.92		$947.9104	$947.91	$947.90	$948.00