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	$240.91	10.364%	$265.8779	$265.88	$265.90	$265.90
Purchase #2	$121.88	7.873%	$131.4756	$131.48	$131.50	$131.50
Purchase #3	$92.87	4.523%	$97.0705	$97.07	$97.05	$97.10
Purchase #4	$246.42	3.844%	$255.8924	$255.89	$255.90	$255.90
Purchase #5	$60.81	8.528%	$65.9959	$66.00	$66.00	$66.00
Purchase #6	$175.88	8.362%	$190.5871	$190.59	$190.60	$190.60
Purchase #7	$82.90	6.261%	$88.0904	$88.09	$88.10	$88.10
7 purchase totals =	$1,021.67		$1,094.9898	$1,095.00	$1,095.05	$1,095.10