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	$225.52	11.225%	$250.8346	$250.83	$250.85	$250.80
Purchase #2	$227.72	8.705%	$247.543	$247.54	$247.55	$247.50
Purchase #3	$139.43	4.567%	$145.7978	$145.80	$145.80	$145.80
Purchase #4	$141.32	7.738%	$152.2553	$152.26	$152.25	$152.30
Purchase #5	$235.88	9.631%	$258.5976	$258.60	$258.60	$258.60
Purchase #6	$35.73	9.220%	$39.0243	$39.02	$39.00	$39.00
Purchase #7	$29.83	5.716%	$31.5351	$31.54	$31.55	$31.50
7 purchase totals =	$1,035.43		$1,125.5877	$1,125.59	$1,125.60	$1,125.50