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	$35.31	4.368%	$36.8523	$36.85	$36.85	$36.90
Purchase #2	$233.79	13.126%	$264.4773	$264.48	$264.50	$264.50
Purchase #3	$13.50	3.665%	$13.9948	$13.99	$14.00	$14.00
Purchase #4	$146.38	9.230%	$159.8909	$159.89	$159.90	$159.90
Purchase #5	$239.75	6.558%	$255.4728	$255.47	$255.45	$255.50
Purchase #6	$63.76	5.177%	$67.0609	$67.06	$67.05	$67.10
Purchase #7	$172.33	11.164%	$191.5689	$191.57	$191.55	$191.60
7 purchase totals =	$904.82		$989.3179	$989.31	$989.30	$989.50