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	$93.85	7.325%	$100.7245	$100.72	$100.70	$100.70
Purchase #2	$204.37	3.495%	$211.5127	$211.51	$211.50	$211.50
Purchase #3	$86.46	6.537%	$92.1119	$92.11	$92.10	$92.10
Purchase #4	$23.50	3.228%	$24.2586	$24.26	$24.25	$24.30
Purchase #5	$221.72	7.716%	$238.8279	$238.83	$238.85	$238.80
Purchase #6	$125.35	4.596%	$131.1111	$131.11	$131.10	$131.10
Purchase #7	$182.27	13.299%	$206.5101	$206.51	$206.50	$206.50
7 purchase totals =	$937.52		$1,005.0568	$1,005.05	$1,005.00	$1,005.00