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	$66.33	11.794%	$74.153	$74.15	$74.15	$74.20
Purchase #2	$35.89	4.730%	$37.5876	$37.59	$37.60	$37.60
Purchase #3	$178.69	3.484%	$184.9156	$184.92	$184.90	$184.90
Purchase #4	$45.56	11.132%	$50.6317	$50.63	$50.65	$50.60
Purchase #5	$206.91	7.732%	$222.9083	$222.91	$222.90	$222.90
Purchase #6	$93.78	8.806%	$102.0383	$102.04	$102.05	$102.00
Purchase #7	$6.35	13.153%	$7.1852	$7.19	$7.20	$7.20
7 purchase totals =	$633.51		$679.4197	$679.43	$679.45	$679.40