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	$100.41	7.591%	$108.0321	$108.03	$108.05	$108.00
Purchase #2	$57.30	4.124%	$59.6631	$59.66	$59.65	$59.70
Purchase #3	$149.99	4.554%	$156.8205	$156.82	$156.80	$156.80
Purchase #4	$70.67	7.571%	$76.0204	$76.02	$76.00	$76.00
Purchase #5	$132.78	6.530%	$141.4505	$141.45	$141.45	$141.50
Purchase #6	$225.78	7.694%	$243.1515	$243.15	$243.15	$243.20
Purchase #7	$230.64	8.146%	$249.4279	$249.43	$249.45	$249.40
7 purchase totals =	$967.57		$1,034.5660	$1,034.56	$1,034.55	$1,034.60