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	$83.87	4.719%	$87.8278	$87.83	$87.85	$87.80
Purchase #2	$75.79	3.586%	$78.5078	$78.51	$78.50	$78.50
Purchase #3	$102.63	5.494%	$108.2685	$108.27	$108.25	$108.30
Purchase #4	$85.48	4.729%	$89.5223	$89.52	$89.50	$89.50
Purchase #5	$228.91	7.664%	$246.4537	$246.45	$246.45	$246.50
Purchase #6	$69.71	5.563%	$73.588	$73.59	$73.60	$73.60
Purchase #7	$40.29	12.442%	$45.3029	$45.30	$45.30	$45.30
7 purchase totals =	$686.68		$729.4710	$729.47	$729.45	$729.50