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	$84.44	7.470%	$90.7477	$90.75	$90.75	$90.70
Purchase #2	$57.69	3.492%	$59.7045	$59.70	$59.70	$59.70
Purchase #3	$114.81	12.345%	$128.9833	$128.98	$129.00	$129.00
Purchase #4	$180.57	9.429%	$197.5959	$197.60	$197.60	$197.60
Purchase #5	$250.89	9.742%	$275.3317	$275.33	$275.35	$275.30
Purchase #6	$157.91	4.480%	$164.9844	$164.98	$165.00	$165.00
Purchase #7	$194.89	10.215%	$214.798	$214.80	$214.80	$214.80
7 purchase totals =	$1,041.20		$1,132.1455	$1,132.14	$1,132.20	$1,132.10