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	$59.57	6.793%	$63.6166	$63.62	$63.60	$63.60
Purchase #2	$182.31	7.789%	$196.5101	$196.51	$196.50	$196.50
Purchase #3	$242.79	12.577%	$273.3257	$273.33	$273.35	$273.30
Purchase #4	$83.46	6.869%	$89.1929	$89.19	$89.20	$89.20
Purchase #5	$143.29	5.502%	$151.1738	$151.17	$151.15	$151.20
Purchase #6	$58.46	7.333%	$62.7469	$62.75	$62.75	$62.70
Purchase #7	$110.88	3.544%	$114.8096	$114.81	$114.80	$114.80
7 purchase totals =	$880.76		$951.3756	$951.38	$951.35	$951.30