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	$194.77	11.111%	$216.4109	$216.41	$216.40	$216.40
Purchase #2	$66.29	8.670%	$72.0373	$72.04	$72.05	$72.00
Purchase #3	$124.89	13.568%	$141.8351	$141.84	$141.85	$141.80
Purchase #4	$124.51	12.831%	$140.4859	$140.49	$140.50	$140.50
Purchase #5	$113.73	4.164%	$118.4657	$118.47	$118.45	$118.50
Purchase #6	$135.90	11.237%	$151.1711	$151.17	$151.15	$151.20
Purchase #7	$161.76	5.363%	$170.4352	$170.44	$170.45	$170.40
7 purchase totals =	$921.85		$1,010.8412	$1,010.86	$1,010.85	$1,010.80