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	$110.33	8.614%	$119.8338	$119.83	$119.85	$119.80
Purchase #2	$78.84	13.161%	$89.2161	$89.22	$89.20	$89.20
Purchase #3	$156.68	10.140%	$172.5674	$172.57	$172.55	$172.60
Purchase #4	$105.97	4.366%	$110.5967	$110.60	$110.60	$110.60
Purchase #5	$94.92	5.146%	$99.8046	$99.80	$99.80	$99.80
Purchase #6	$247.60	9.484%	$271.0824	$271.08	$271.10	$271.10
Purchase #7	$37.94	12.203%	$42.5698	$42.57	$42.55	$42.60
7 purchase totals =	$832.28		$905.6708	$905.67	$905.65	$905.70