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	$94.82	4.549%	$99.1334	$99.13	$99.15	$99.10
Purchase #2	$85.90	4.779%	$90.0052	$90.01	$90.00	$90.00
Purchase #3	$136.51	13.438%	$154.8542	$154.85	$154.85	$154.90
Purchase #4	$102.96	6.507%	$109.6596	$109.66	$109.65	$109.70
Purchase #5	$151.50	6.440%	$161.2566	$161.26	$161.25	$161.30
Purchase #6	$116.37	7.564%	$125.1722	$125.17	$125.15	$125.20
Purchase #7	$176.37	5.283%	$185.6876	$185.69	$185.70	$185.70
7 purchase totals =	$864.43		$925.7688	$925.77	$925.75	$925.90