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	$210.39	11.591%	$234.7763	$234.78	$234.80	$234.80
Purchase #2	$231.60	5.292%	$243.8563	$243.86	$243.85	$243.90
Purchase #3	$76.67	11.636%	$85.5913	$85.59	$85.60	$85.60
Purchase #4	$101.51	12.161%	$113.8546	$113.85	$113.85	$113.90
Purchase #5	$125.56	8.620%	$136.3833	$136.38	$136.40	$136.40
Purchase #6	$174.37	13.782%	$198.4017	$198.40	$198.40	$198.40
Purchase #7	$6.34	11.472%	$7.0673	$7.07	$7.05	$7.10
7 purchase totals =	$926.44		$1,019.9308	$1,019.93	$1,019.95	$1,020.10