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	$212.96	7.640%	$229.2301	$229.23	$229.25	$229.20
Purchase #2	$76.58	8.846%	$83.3543	$83.35	$83.35	$83.40
Purchase #3	$217.41	4.611%	$227.4348	$227.43	$227.45	$227.40
Purchase #4	$34.43	11.740%	$38.4721	$38.47	$38.45	$38.50
Purchase #5	$248.60	3.333%	$256.8858	$256.89	$256.90	$256.90
Purchase #6	$6.25	13.649%	$7.1031	$7.10	$7.10	$7.10
Purchase #7	$160.41	6.200%	$170.3554	$170.36	$170.35	$170.40
7 purchase totals =	$956.64		$1,012.8356	$1,012.83	$1,012.85	$1,012.90