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	$144.90	10.734%	$160.4536	$160.45	$160.45	$160.50
Purchase #2	$169.53	8.851%	$184.5351	$184.54	$184.55	$184.50
Purchase #3	$114.60	11.600%	$127.8936	$127.89	$127.90	$127.90
Purchase #4	$215.84	12.685%	$243.2193	$243.22	$243.20	$243.20
Purchase #5	$179.30	13.675%	$203.8193	$203.82	$203.80	$203.80
Purchase #6	$111.93	5.287%	$117.8477	$117.85	$117.85	$117.80
Purchase #7	$103.43	4.728%	$108.3202	$108.32	$108.30	$108.30
7 purchase totals =	$1,039.53		$1,146.0888	$1,146.09	$1,146.05	$1,146.00