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	$183.73	6.626%	$195.9039	$195.90	$195.90	$195.90
Purchase #2	$154.67	13.710%	$175.8753	$175.88	$175.90	$175.90
Purchase #3	$145.68	5.252%	$153.3311	$153.33	$153.35	$153.30
Purchase #4	$95.82	3.258%	$98.9418	$98.94	$98.95	$98.90
Purchase #5	$133.31	6.363%	$141.7925	$141.79	$141.80	$141.80
Purchase #6	$37.61	13.389%	$42.6456	$42.65	$42.65	$42.60
Purchase #7	$75.61	12.429%	$85.0076	$85.01	$85.00	$85.00
7 purchase totals =	$826.43		$893.4978	$893.50	$893.55	$893.40