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	$118.52	11.149%	$131.7338	$131.73	$131.75	$131.70
Purchase #2	$147.36	10.709%	$163.1408	$163.14	$163.15	$163.10
Purchase #3	$73.57	11.552%	$82.0688	$82.07	$82.05	$82.10
Purchase #4	$136.52	10.243%	$150.5037	$150.50	$150.50	$150.50
Purchase #5	$50.74	7.441%	$54.5156	$54.52	$54.50	$54.50
Purchase #6	$177.35	8.325%	$192.1144	$192.11	$192.10	$192.10
Purchase #7	$169.29	12.511%	$190.4699	$190.47	$190.45	$190.50
7 purchase totals =	$873.35		$964.5470	$964.54	$964.50	$964.50