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	$114.27	10.666%	$126.458	$126.46	$126.45	$126.50
Purchase #2	$31.42	9.125%	$34.2871	$34.29	$34.30	$34.30
Purchase #3	$135.71	12.624%	$152.842	$152.84	$152.85	$152.80
Purchase #4	$160.39	7.816%	$172.9261	$172.93	$172.95	$172.90
Purchase #5	$98.49	4.782%	$103.1998	$103.20	$103.20	$103.20
Purchase #6	$90.73	13.406%	$102.8933	$102.89	$102.90	$102.90
Purchase #7	$237.82	3.204%	$245.4398	$245.44	$245.45	$245.40
7 purchase totals =	$868.83		$938.0461	$938.05	$938.10	$938.00