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	$196.86	6.452%	$209.5614	$209.56	$209.55	$209.60
Purchase #2	$217.54	6.544%	$231.7758	$231.78	$231.80	$231.80
Purchase #3	$94.59	5.871%	$100.1434	$100.14	$100.15	$100.10
Purchase #4	$81.64	10.281%	$90.0334	$90.03	$90.05	$90.00
Purchase #5	$17.64	7.781%	$19.0126	$19.01	$19.00	$19.00
Purchase #6	$227.46	11.182%	$252.8946	$252.89	$252.90	$252.90
Purchase #7	$224.70	5.798%	$237.7281	$237.73	$237.75	$237.70
7 purchase totals =	$1,060.43		$1,141.1493	$1,141.14	$1,141.20	$1,141.10