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	$224.46	11.706%	$250.7353	$250.74	$250.75	$250.70
Purchase #2	$175.86	5.143%	$184.9045	$184.90	$184.90	$184.90
Purchase #3	$65.96	6.847%	$70.4763	$70.48	$70.50	$70.50
Purchase #4	$22.55	6.822%	$24.0884	$24.09	$24.10	$24.10
Purchase #5	$81.49	11.520%	$90.8776	$90.88	$90.90	$90.90
Purchase #6	$171.55	6.284%	$182.3302	$182.33	$182.35	$182.30
Purchase #7	$130.85	6.694%	$139.6091	$139.61	$139.60	$139.60
7 purchase totals =	$872.72		$943.0214	$943.03	$943.10	$943.00