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	$234.71	9.279%	$256.4887	$256.49	$256.50	$256.50
Purchase #2	$120.77	8.503%	$131.0391	$131.04	$131.05	$131.00
Purchase #3	$159.70	7.834%	$172.2109	$172.21	$172.20	$172.20
Purchase #4	$207.37	3.394%	$214.4081	$214.41	$214.40	$214.40
Purchase #5	$58.43	5.507%	$61.6477	$61.65	$61.65	$61.60
Purchase #6	$181.32	10.750%	$200.8119	$200.81	$200.80	$200.80
Purchase #7	$84.60	5.798%	$89.5051	$89.51	$89.50	$89.50
7 purchase totals =	$1,046.90		$1,126.1115	$1,126.12	$1,126.10	$1,126.00