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	$51.32	10.596%	$56.7579	$56.76	$56.75	$56.80
Purchase #2	$221.71	4.634%	$231.984	$231.98	$232.00	$232.00
Purchase #3	$123.60	5.628%	$130.5562	$130.56	$130.55	$130.60
Purchase #4	$141.32	12.837%	$159.4612	$159.46	$159.45	$159.50
Purchase #5	$246.29	10.385%	$271.8672	$271.87	$271.85	$271.90
Purchase #6	$151.25	12.703%	$170.4633	$170.46	$170.45	$170.50
Purchase #7	$29.89	6.196%	$31.742	$31.74	$31.75	$31.70
7 purchase totals =	$965.38		$1,052.8318	$1,052.83	$1,052.80	$1,053.00