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	$110.61	3.489%	$114.4692	$114.47	$114.45	$114.50
Purchase #2	$169.25	5.664%	$178.8363	$178.84	$178.85	$178.80
Purchase #3	$102.57	9.692%	$112.5111	$112.51	$112.50	$112.50
Purchase #4	$101.83	8.471%	$110.456	$110.46	$110.45	$110.50
Purchase #5	$12.58	10.211%	$13.8645	$13.86	$13.85	$13.90
Purchase #6	$61.51	3.327%	$63.5564	$63.56	$63.55	$63.60
Purchase #7	$143.78	4.735%	$150.588	$150.59	$150.60	$150.60
7 purchase totals =	$702.13		$744.2815	$744.29	$744.25	$744.40