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	$209.67	8.479%	$227.4479	$227.45	$227.45	$227.40
Purchase #2	$85.38	5.849%	$90.3739	$90.37	$90.35	$90.40
Purchase #3	$156.89	9.691%	$172.0942	$172.09	$172.10	$172.10
Purchase #4	$39.33	9.682%	$43.1379	$43.14	$43.15	$43.10
Purchase #5	$143.61	10.409%	$158.5584	$158.56	$158.55	$158.60
Purchase #6	$170.45	8.527%	$184.9843	$184.98	$185.00	$185.00
Purchase #7	$118.49	3.673%	$122.8421	$122.84	$122.85	$122.80
7 purchase totals =	$923.82		$999.4387	$999.43	$999.45	$999.40