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	$78.91	7.817%	$85.0784	$85.08	$85.10	$85.10
Purchase #2	$21.42	11.430%	$23.8683	$23.87	$23.85	$23.90
Purchase #3	$72.63	8.291%	$78.6518	$78.65	$78.65	$78.70
Purchase #4	$109.39	11.645%	$122.1285	$122.13	$122.15	$122.10
Purchase #5	$105.85	13.296%	$119.9238	$119.92	$119.90	$119.90
Purchase #6	$146.87	11.709%	$164.067	$164.07	$164.05	$164.10
Purchase #7	$89.25	11.833%	$99.811	$99.81	$99.80	$99.80
7 purchase totals =	$624.32		$693.5288	$693.53	$693.50	$693.60