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	$140.63	7.724%	$151.4923	$151.49	$151.50	$151.50
Purchase #2	$166.78	6.378%	$177.4172	$177.42	$177.40	$177.40
Purchase #3	$6.75	3.865%	$7.0109	$7.01	$7.00	$7.00
Purchase #4	$75.77	13.420%	$85.9383	$85.94	$85.95	$85.90
Purchase #5	$60.28	5.490%	$63.5894	$63.59	$63.60	$63.60
Purchase #6	$65.97	8.114%	$71.3228	$71.32	$71.30	$71.30
Purchase #7	$105.57	6.650%	$112.5904	$112.59	$112.60	$112.60
7 purchase totals =	$621.75		$669.3613	$669.36	$669.35	$669.30