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 $41.32   13.252%   $46.7957   $46.80   $46.80   $46.80  
  Purchase #2 $163.37   6.244%   $173.5708   $173.57   $173.55   $173.60  
  Purchase #3 $195.86   5.578%   $206.7851   $206.79   $206.80   $206.80  
  Purchase #4 $242.27   13.840%   $275.8002   $275.80   $275.80   $275.80  
  Purchase #5 $241.84   12.697%   $272.5464   $272.55   $272.55   $272.50  
  Purchase #6 $35.25   5.368%   $37.1422   $37.14   $37.15   $37.10  
  Purchase #7 $238.44   3.404%   $246.5565   $246.56   $246.55   $246.60  
  7 purchase totals = $1,158.35       $1,259.1969   $1,259.21   $1,259.20   $1,259.20