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	$133.50	11.500%	$148.8525	$148.85	$148.85	$148.90
Purchase #2	$72.46	11.380%	$80.7059	$80.71	$80.70	$80.70
Purchase #3	$136.81	10.823%	$151.6169	$151.62	$151.60	$151.60
Purchase #4	$69.91	5.685%	$73.8844	$73.88	$73.90	$73.90
Purchase #5	$142.54	5.648%	$150.5907	$150.59	$150.60	$150.60
Purchase #6	$234.82	4.825%	$246.1501	$246.15	$246.15	$246.20
Purchase #7	$8.41	5.241%	$8.8508	$8.85	$8.85	$8.90
7 purchase totals =	$798.45		$860.6513	$860.65	$860.65	$860.80