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	$112.43	13.265%	$127.3438	$127.34	$127.35	$127.30
Purchase #2	$114.88	8.265%	$124.3748	$124.37	$124.35	$124.40
Purchase #3	$213.57	13.123%	$241.5968	$241.60	$241.60	$241.60
Purchase #4	$247.66	12.331%	$278.199	$278.20	$278.20	$278.20
Purchase #5	$16.98	6.744%	$18.1251	$18.13	$18.15	$18.10
Purchase #6	$250.63	13.691%	$284.9438	$284.94	$284.95	$284.90
Purchase #7	$93.76	7.268%	$100.5745	$100.57	$100.55	$100.60
7 purchase totals =	$1,049.91		$1,175.1578	$1,175.15	$1,175.15	$1,175.10