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	$138.32	10.483%	$152.8201	$152.82	$152.80	$152.80
Purchase #2	$200.43	5.119%	$210.69	$210.69	$210.70	$210.70
Purchase #3	$69.38	4.445%	$72.4639	$72.46	$72.45	$72.50
Purchase #4	$76.96	11.127%	$85.5233	$85.52	$85.50	$85.50
Purchase #5	$106.50	12.340%	$119.6421	$119.64	$119.65	$119.60
Purchase #6	$197.64	9.379%	$216.1767	$216.18	$216.20	$216.20
Purchase #7	$113.39	12.695%	$127.7849	$127.78	$127.80	$127.80
7 purchase totals =	$902.62		$985.1010	$985.09	$985.10	$985.10