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	$116.54	9.385%	$127.4773	$127.48	$127.50	$127.50
Purchase #2	$30.92	5.119%	$32.5028	$32.50	$32.50	$32.50
Purchase #3	$82.57	13.593%	$93.7937	$93.79	$93.80	$93.80
Purchase #4	$150.89	9.735%	$165.5791	$165.58	$165.60	$165.60
Purchase #5	$164.57	13.790%	$187.2642	$187.26	$187.25	$187.30
Purchase #6	$72.88	4.124%	$75.8856	$75.89	$75.90	$75.90
Purchase #7	$114.77	5.735%	$121.3521	$121.35	$121.35	$121.40
7 purchase totals =	$733.14		$803.8548	$803.85	$803.90	$804.00