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	$101.65	4.243%	$105.963	$105.96	$105.95	$106.00
Purchase #2	$108.79	13.406%	$123.3744	$123.37	$123.35	$123.40
Purchase #3	$94.60	11.252%	$105.2444	$105.24	$105.25	$105.20
Purchase #4	$250.47	4.296%	$261.2302	$261.23	$261.25	$261.20
Purchase #5	$234.60	6.519%	$249.8936	$249.89	$249.90	$249.90
Purchase #6	$12.43	6.167%	$13.1966	$13.20	$13.20	$13.20
Purchase #7	$100.76	8.695%	$109.5211	$109.52	$109.50	$109.50
7 purchase totals =	$903.30		$968.4233	$968.41	$968.40	$968.40