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	$144.85	4.653%	$151.5899	$151.59	$151.60	$151.60
Purchase #2	$92.29	8.602%	$100.2288	$100.23	$100.25	$100.20
Purchase #3	$197.44	8.569%	$214.3586	$214.36	$214.35	$214.40
Purchase #4	$89.60	8.814%	$97.4973	$97.50	$97.50	$97.50
Purchase #5	$108.97	13.691%	$123.8891	$123.89	$123.90	$123.90
Purchase #6	$72.70	13.811%	$82.7406	$82.74	$82.75	$82.70
Purchase #7	$167.88	11.518%	$187.2164	$187.22	$187.20	$187.20
7 purchase totals =	$873.73		$957.5207	$957.53	$957.55	$957.50