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	$86.35	3.330%	$89.2255	$89.23	$89.25	$89.20
Purchase #2	$131.76	10.229%	$145.2377	$145.24	$145.25	$145.20
Purchase #3	$229.40	8.323%	$248.493	$248.49	$248.50	$248.50
Purchase #4	$88.90	6.784%	$94.931	$94.93	$94.95	$94.90
Purchase #5	$58.78	4.659%	$61.5186	$61.52	$61.50	$61.50
Purchase #6	$227.85	12.577%	$256.5067	$256.51	$256.50	$256.50
Purchase #7	$135.95	11.554%	$151.6577	$151.66	$151.65	$151.70
7 purchase totals =	$958.99		$1,047.5702	$1,047.58	$1,047.60	$1,047.50