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	$235.53	12.166%	$264.1846	$264.18	$264.20	$264.20
Purchase #2	$31.53	7.169%	$33.7904	$33.79	$33.80	$33.80
Purchase #3	$228.33	3.612%	$236.5773	$236.58	$236.60	$236.60
Purchase #4	$42.66	3.370%	$44.0976	$44.10	$44.10	$44.10
Purchase #5	$225.96	12.576%	$254.3767	$254.38	$254.40	$254.40
Purchase #6	$169.49	13.520%	$192.405	$192.41	$192.40	$192.40
Purchase #7	$112.83	12.584%	$127.0285	$127.03	$127.05	$127.00
7 purchase totals =	$1,046.33		$1,152.4601	$1,152.47	$1,152.55	$1,152.50