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	$145.71	7.114%	$156.0758	$156.08	$156.10	$156.10
Purchase #2	$165.81	6.378%	$176.3854	$176.39	$176.40	$176.40
Purchase #3	$31.40	4.737%	$32.8874	$32.89	$32.90	$32.90
Purchase #4	$10.39	9.195%	$11.3454	$11.35	$11.35	$11.30
Purchase #5	$175.31	5.465%	$184.8907	$184.89	$184.90	$184.90
Purchase #6	$53.63	9.102%	$58.5114	$58.51	$58.50	$58.50
Purchase #7	$86.50	9.634%	$94.8334	$94.83	$94.85	$94.80
7 purchase totals =	$668.75		$714.9295	$714.94	$715.00	$714.90