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	$20.32	10.418%	$22.4369	$22.44	$22.45	$22.40
Purchase #2	$140.66	8.414%	$152.4951	$152.50	$152.50	$152.50
Purchase #3	$237.85	6.580%	$253.5005	$253.50	$253.50	$253.50
Purchase #4	$124.62	5.403%	$131.3532	$131.35	$131.35	$131.40
Purchase #5	$205.55	11.711%	$229.622	$229.62	$229.60	$229.60
Purchase #6	$90.72	11.385%	$101.0485	$101.05	$101.05	$101.00
Purchase #7	$9.90	5.786%	$10.4728	$10.47	$10.45	$10.50
7 purchase totals =	$829.62		$900.9290	$900.93	$900.90	$900.90