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	$90.30	7.773%	$97.319	$97.32	$97.30	$97.30
Purchase #2	$110.81	7.656%	$119.2936	$119.29	$119.30	$119.30
Purchase #3	$9.88	9.865%	$10.8547	$10.85	$10.85	$10.90
Purchase #4	$69.42	3.569%	$71.8976	$71.90	$71.90	$71.90
Purchase #5	$239.93	8.130%	$259.4363	$259.44	$259.45	$259.40
Purchase #6	$78.88	13.198%	$89.2906	$89.29	$89.30	$89.30
Purchase #7	$80.36	9.311%	$87.8423	$87.84	$87.85	$87.80
7 purchase totals =	$679.58		$735.9341	$735.93	$735.95	$735.90