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	$200.86	3.579%	$208.0488	$208.05	$208.05	$208.00
Purchase #2	$84.47	4.189%	$88.0084	$88.01	$88.00	$88.00
Purchase #3	$174.90	13.726%	$198.9068	$198.91	$198.90	$198.90
Purchase #4	$10.68	13.757%	$12.1492	$12.15	$12.15	$12.10
Purchase #5	$238.60	11.328%	$265.6286	$265.63	$265.65	$265.60
Purchase #6	$125.60	4.511%	$131.2658	$131.27	$131.25	$131.30
Purchase #7	$69.49	7.516%	$74.7129	$74.71	$74.70	$74.70
7 purchase totals =	$904.60		$978.7205	$978.73	$978.70	$978.60