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	$85.94	8.635%	$93.3609	$93.36	$93.35	$93.40
Purchase #2	$95.36	5.198%	$100.3168	$100.32	$100.30	$100.30
Purchase #3	$215.39	3.494%	$222.9157	$222.92	$222.90	$222.90
Purchase #4	$43.55	11.228%	$48.4398	$48.44	$48.45	$48.40
Purchase #5	$96.96	8.811%	$105.5031	$105.50	$105.50	$105.50
Purchase #6	$81.58	10.484%	$90.1328	$90.13	$90.15	$90.10
Purchase #7	$75.44	7.516%	$81.1101	$81.11	$81.10	$81.10
7 purchase totals =	$694.22		$741.7792	$741.78	$741.75	$741.70