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	$134.67	7.697%	$145.0355	$145.04	$145.05	$145.00
Purchase #2	$134.33	6.562%	$143.1447	$143.14	$143.15	$143.10
Purchase #3	$119.83	9.507%	$131.2222	$131.22	$131.20	$131.20
Purchase #4	$157.68	11.527%	$175.8558	$175.86	$175.85	$175.90
Purchase #5	$73.53	8.554%	$79.8198	$79.82	$79.80	$79.80
Purchase #6	$69.48	4.207%	$72.403	$72.40	$72.40	$72.40
Purchase #7	$139.38	8.432%	$151.1325	$151.13	$151.15	$151.10
7 purchase totals =	$828.90		$898.6135	$898.61	$898.60	$898.50