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	$107.43	10.325%	$118.5221	$118.52	$118.50	$118.50
Purchase #2	$161.42	4.345%	$168.4337	$168.43	$168.45	$168.40
Purchase #3	$250.53	10.154%	$275.9688	$275.97	$275.95	$276.00
Purchase #4	$250.67	5.215%	$263.7424	$263.74	$263.75	$263.70
Purchase #5	$84.46	11.202%	$93.9212	$93.92	$93.90	$93.90
Purchase #6	$180.65	4.701%	$189.1424	$189.14	$189.15	$189.10
Purchase #7	$36.34	11.375%	$40.4737	$40.47	$40.45	$40.50
7 purchase totals =	$1,071.50		$1,150.2043	$1,150.19	$1,150.15	$1,150.10