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	$63.55	13.375%	$72.0498	$72.05	$72.05	$72.00
Purchase #2	$101.38	4.688%	$106.1327	$106.13	$106.15	$106.10
Purchase #3	$94.32	5.663%	$99.6613	$99.66	$99.65	$99.70
Purchase #4	$216.94	12.695%	$244.4805	$244.48	$244.50	$244.50
Purchase #5	$108.49	6.103%	$115.1111	$115.11	$115.10	$115.10
Purchase #6	$139.67	8.547%	$151.6076	$151.61	$151.60	$151.60
Purchase #7	$136.46	6.494%	$145.3217	$145.32	$145.30	$145.30
7 purchase totals =	$860.81		$934.3647	$934.36	$934.35	$934.30