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	$217.70	4.813%	$228.1779	$228.18	$228.20	$228.20
Purchase #2	$95.30	6.300%	$101.3039	$101.30	$101.30	$101.30
Purchase #3	$35.71	3.164%	$36.8399	$36.84	$36.85	$36.80
Purchase #4	$95.61	4.527%	$99.9383	$99.94	$99.95	$99.90
Purchase #5	$164.39	5.192%	$172.9251	$172.93	$172.95	$172.90
Purchase #6	$215.85	6.323%	$229.4982	$229.50	$229.50	$229.50
Purchase #7	$13.42	3.536%	$13.8945	$13.89	$13.90	$13.90
7 purchase totals =	$837.98		$882.5778	$882.58	$882.65	$882.50