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	$95.91	3.106%	$98.889	$98.89	$98.90	$98.90
Purchase #2	$38.55	5.557%	$40.6922	$40.69	$40.70	$40.70
Purchase #3	$12.32	7.142%	$13.1999	$13.20	$13.20	$13.20
Purchase #4	$223.53	3.678%	$231.7514	$231.75	$231.75	$231.80
Purchase #5	$199.81	11.555%	$222.898	$222.90	$222.90	$222.90
Purchase #6	$196.35	5.348%	$206.8508	$206.85	$206.85	$206.90
Purchase #7	$163.62	11.738%	$182.8257	$182.83	$182.85	$182.80
7 purchase totals =	$930.09		$997.1070	$997.11	$997.15	$997.20