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 $63.56   8.502%   $68.9639   $68.96   $68.95   $69.00  
  Purchase #2 $121.60   9.867%   $133.5983   $133.60   $133.60   $133.60  
  Purchase #3 $188.55   5.835%   $199.5519   $199.55   $199.55   $199.60  
  Purchase #4 $207.64   5.574%   $219.2139   $219.21   $219.20   $219.20  
  Purchase #5 $179.81   9.235%   $196.4155   $196.42   $196.40   $196.40  
  Purchase #6 $197.50   5.151%   $207.6732   $207.67   $207.65   $207.70  
  Purchase #7 $118.91   5.237%   $125.1373   $125.14   $125.15   $125.10  
  7 purchase totals = $1,077.57       $1,150.5540   $1,150.55   $1,150.50   $1,150.60