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	$175.77	11.530%	$196.0363	$196.04	$196.05	$196.00
Purchase #2	$41.67	12.556%	$46.9021	$46.90	$46.90	$46.90
Purchase #3	$227.59	6.428%	$242.2195	$242.22	$242.20	$242.20
Purchase #4	$249.50	10.166%	$274.8642	$274.86	$274.85	$274.90
Purchase #5	$12.46	3.426%	$12.8869	$12.89	$12.90	$12.90
Purchase #6	$6.72	11.425%	$7.4878	$7.49	$7.50	$7.50
Purchase #7	$146.36	11.403%	$163.0494	$163.05	$163.05	$163.00
7 purchase totals =	$860.07		$943.4462	$943.45	$943.45	$943.40