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	$212.44	3.456%	$219.7819	$219.78	$219.80	$219.80
Purchase #2	$77.78	7.563%	$83.6625	$83.66	$83.65	$83.70
Purchase #3	$210.39	13.830%	$239.4869	$239.49	$239.50	$239.50
Purchase #4	$188.99	4.107%	$196.7518	$196.75	$196.75	$196.80
Purchase #5	$169.60	12.159%	$190.2217	$190.22	$190.20	$190.20
Purchase #6	$215.73	10.400%	$238.1659	$238.17	$238.15	$238.20
Purchase #7	$74.78	5.559%	$78.937	$78.94	$78.95	$78.90
7 purchase totals =	$1,149.71		$1,247.0077	$1,247.01	$1,247.00	$1,247.10