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	$198.51	7.211%	$212.8246	$212.82	$212.80	$212.80
Purchase #2	$164.82	5.266%	$173.4994	$173.50	$173.50	$173.50
Purchase #3	$55.43	7.257%	$59.4526	$59.45	$59.45	$59.50
Purchase #4	$98.50	12.216%	$110.5328	$110.53	$110.55	$110.50
Purchase #5	$50.43	9.497%	$55.2193	$55.22	$55.20	$55.20
Purchase #6	$100.73	3.319%	$104.0732	$104.07	$104.05	$104.10
Purchase #7	$44.83	10.421%	$49.5017	$49.50	$49.50	$49.50
7 purchase totals =	$713.25		$765.1036	$765.09	$765.05	$765.10