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	$152.82	11.654%	$170.6296	$170.63	$170.65	$170.60
Purchase #2	$176.60	11.239%	$196.4481	$196.45	$196.45	$196.40
Purchase #3	$93.33	13.476%	$105.9072	$105.91	$105.90	$105.90
Purchase #4	$66.60	9.741%	$73.0875	$73.09	$73.10	$73.10
Purchase #5	$165.67	4.589%	$173.2726	$173.27	$173.25	$173.30
Purchase #6	$89.26	7.271%	$95.7501	$95.75	$95.75	$95.80
Purchase #7	$92.66	7.817%	$99.9032	$99.90	$99.90	$99.90
7 purchase totals =	$836.94		$914.9983	$915.00	$915.00	$915.00