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	$193.53	6.682%	$206.4617	$206.46	$206.45	$206.50
Purchase #2	$219.42	10.318%	$242.0598	$242.06	$242.05	$242.10
Purchase #3	$36.60	11.555%	$40.8291	$40.83	$40.85	$40.80
Purchase #4	$244.57	5.325%	$257.5934	$257.59	$257.60	$257.60
Purchase #5	$203.40	9.333%	$222.3833	$222.38	$222.40	$222.40
Purchase #6	$41.76	8.451%	$45.2891	$45.29	$45.30	$45.30
Purchase #7	$10.72	10.197%	$11.8131	$11.81	$11.80	$11.80
7 purchase totals =	$950.00		$1,026.4295	$1,026.42	$1,026.45	$1,026.50