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	$184.86	8.510%	$200.5916	$200.59	$200.60	$200.60
Purchase #2	$242.50	5.320%	$255.401	$255.40	$255.40	$255.40
Purchase #3	$113.61	5.329%	$119.6643	$119.66	$119.65	$119.70
Purchase #4	$47.65	4.812%	$49.9429	$49.94	$49.95	$49.90
Purchase #5	$249.79	8.634%	$271.3569	$271.36	$271.35	$271.40
Purchase #6	$140.86	13.208%	$159.4648	$159.46	$159.45	$159.50
Purchase #7	$30.67	12.229%	$34.4206	$34.42	$34.40	$34.40
7 purchase totals =	$1,009.94		$1,090.8421	$1,090.83	$1,090.80	$1,090.90