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	$174.73	12.215%	$196.0733	$196.07	$196.05	$196.10
Purchase #2	$119.65	5.324%	$126.0202	$126.02	$126.00	$126.00
Purchase #3	$160.31	12.676%	$180.6309	$180.63	$180.65	$180.60
Purchase #4	$74.82	6.569%	$79.7349	$79.73	$79.75	$79.70
Purchase #5	$197.39	11.325%	$219.7444	$219.74	$219.75	$219.70
Purchase #6	$52.65	13.590%	$59.8051	$59.81	$59.80	$59.80
Purchase #7	$78.78	12.833%	$88.8898	$88.89	$88.90	$88.90
7 purchase totals =	$858.33		$950.8986	$950.89	$950.90	$950.80