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	$96.76	13.567%	$109.8874	$109.89	$109.90	$109.90
Purchase #2	$165.94	8.707%	$180.3884	$180.39	$180.40	$180.40
Purchase #3	$23.53	9.325%	$25.7242	$25.72	$25.70	$25.70
Purchase #4	$249.40	6.772%	$266.2894	$266.29	$266.30	$266.30
Purchase #5	$18.88	13.105%	$21.3542	$21.35	$21.35	$21.40
Purchase #6	$248.42	10.740%	$275.1003	$275.10	$275.10	$275.10
Purchase #7	$155.53	5.697%	$164.3905	$164.39	$164.40	$164.40
7 purchase totals =	$958.46		$1,043.1344	$1,043.13	$1,043.15	$1,043.20