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	$141.89	6.371%	$150.9298	$150.93	$150.95	$150.90
Purchase #2	$239.61	13.316%	$271.5165	$271.52	$271.50	$271.50
Purchase #3	$33.73	10.484%	$37.2663	$37.27	$37.25	$37.30
Purchase #4	$140.56	9.172%	$153.4522	$153.45	$153.45	$153.50
Purchase #5	$22.61	4.459%	$23.6182	$23.62	$23.60	$23.60
Purchase #6	$95.41	7.151%	$102.2328	$102.23	$102.25	$102.20
Purchase #7	$132.83	10.220%	$146.4052	$146.41	$146.40	$146.40
7 purchase totals =	$806.64		$885.4210	$885.43	$885.40	$885.40