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	$106.63	11.196%	$118.5683	$118.57	$118.55	$118.60
Purchase #2	$187.61	13.810%	$213.5189	$213.52	$213.50	$213.50
Purchase #3	$70.27	11.393%	$78.2759	$78.28	$78.30	$78.30
Purchase #4	$104.72	8.580%	$113.705	$113.71	$113.70	$113.70
Purchase #5	$190.58	4.421%	$199.0055	$199.01	$199.00	$199.00
Purchase #6	$90.52	5.733%	$95.7095	$95.71	$95.70	$95.70
Purchase #7	$154.28	11.243%	$171.6257	$171.63	$171.65	$171.60
7 purchase totals =	$904.61		$990.4088	$990.43	$990.40	$990.40