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	$138.43	9.696%	$151.8522	$151.85	$151.85	$151.90
Purchase #2	$216.58	3.204%	$223.5192	$223.52	$223.50	$223.50
Purchase #3	$145.58	4.538%	$152.1864	$152.19	$152.20	$152.20
Purchase #4	$50.72	8.642%	$55.1032	$55.10	$55.10	$55.10
Purchase #5	$200.75	4.675%	$210.1351	$210.14	$210.15	$210.10
Purchase #6	$185.61	13.417%	$210.5133	$210.51	$210.50	$210.50
Purchase #7	$100.94	12.846%	$113.9068	$113.91	$113.90	$113.90
7 purchase totals =	$1,038.61		$1,117.2162	$1,117.22	$1,117.20	$1,117.20