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	$191.43	12.802%	$215.9369	$215.94	$215.95	$215.90
Purchase #2	$78.35	6.591%	$83.514	$83.51	$83.50	$83.50
Purchase #3	$35.43	5.681%	$37.4428	$37.44	$37.45	$37.40
Purchase #4	$85.78	5.665%	$90.6394	$90.64	$90.65	$90.60
Purchase #5	$99.26	8.604%	$107.8003	$107.80	$107.80	$107.80
Purchase #6	$32.93	4.501%	$34.4122	$34.41	$34.40	$34.40
Purchase #7	$22.42	8.235%	$24.2663	$24.27	$24.25	$24.30
7 purchase totals =	$545.60		$594.0119	$594.01	$594.00	$593.90