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	$224.93	7.750%	$242.3621	$242.36	$242.35	$242.40
Purchase #2	$141.91	11.674%	$158.4766	$158.48	$158.50	$158.50
Purchase #3	$134.35	3.643%	$139.2444	$139.24	$139.25	$139.20
Purchase #4	$208.43	8.157%	$225.4316	$225.43	$225.45	$225.40
Purchase #5	$50.28	8.673%	$54.6408	$54.64	$54.65	$54.60
Purchase #6	$140.50	3.161%	$144.9412	$144.94	$144.95	$144.90
Purchase #7	$96.43	7.448%	$103.6121	$103.61	$103.60	$103.60
7 purchase totals =	$996.83		$1,068.7088	$1,068.70	$1,068.75	$1,068.60