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	$112.28	9.511%	$122.959	$122.96	$122.95	$123.00
Purchase #2	$209.30	10.569%	$231.4209	$231.42	$231.40	$231.40
Purchase #3	$73.96	10.729%	$81.8952	$81.90	$81.90	$81.90
Purchase #4	$178.32	6.624%	$190.1319	$190.13	$190.15	$190.10
Purchase #5	$179.61	9.440%	$196.5652	$196.57	$196.55	$196.60
Purchase #6	$48.73	8.484%	$52.8643	$52.86	$52.85	$52.90
Purchase #7	$19.77	3.707%	$20.5029	$20.50	$20.50	$20.50
7 purchase totals =	$821.97		$896.3394	$896.34	$896.30	$896.40