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	$214.85	8.272%	$232.6224	$232.62	$232.60	$232.60
Purchase #2	$155.73	10.614%	$172.2592	$172.26	$172.25	$172.30
Purchase #3	$198.87	12.370%	$223.4702	$223.47	$223.45	$223.50
Purchase #4	$140.36	9.283%	$153.3896	$153.39	$153.40	$153.40
Purchase #5	$84.50	12.633%	$95.1749	$95.17	$95.15	$95.20
Purchase #6	$249.39	12.642%	$280.9179	$280.92	$280.90	$280.90
Purchase #7	$197.57	13.110%	$223.4714	$223.47	$223.45	$223.50
7 purchase totals =	$1,241.27		$1,381.3056	$1,381.30	$1,381.20	$1,381.40