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	$154.42	9.110%	$168.4877	$168.49	$168.50	$168.50
Purchase #2	$140.43	10.572%	$155.2763	$155.28	$155.30	$155.30
Purchase #3	$235.51	6.787%	$251.4941	$251.49	$251.50	$251.50
Purchase #4	$198.48	9.180%	$216.7005	$216.70	$216.70	$216.70
Purchase #5	$33.42	13.553%	$37.9494	$37.95	$37.95	$37.90
Purchase #6	$139.89	11.610%	$156.1312	$156.13	$156.15	$156.10
Purchase #7	$38.87	8.354%	$42.1172	$42.12	$42.10	$42.10
7 purchase totals =	$941.02		$1,028.1564	$1,028.16	$1,028.20	$1,028.10