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	$46.51	12.775%	$52.4517	$52.45	$52.45	$52.50
Purchase #2	$17.39	11.224%	$19.3419	$19.34	$19.35	$19.30
Purchase #3	$104.32	4.339%	$108.8464	$108.85	$108.85	$108.80
Purchase #4	$85.74	3.189%	$88.4742	$88.47	$88.45	$88.50
Purchase #5	$213.38	4.148%	$222.231	$222.23	$222.25	$222.20
Purchase #6	$221.80	5.117%	$233.1495	$233.15	$233.15	$233.10
Purchase #7	$102.29	6.593%	$109.034	$109.03	$109.05	$109.00
7 purchase totals =	$791.43		$833.5287	$833.52	$833.55	$833.40