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 $92.98   13.397%   $105.4365   $105.44   $105.45   $105.40  
  Purchase #2 $215.25   12.152%   $241.4072   $241.41   $241.40   $241.40  
  Purchase #3 $55.41   4.605%   $57.9616   $57.96   $57.95   $58.00  
  Purchase #4 $244.65   12.568%   $275.3976   $275.40   $275.40   $275.40  
  Purchase #5 $223.85   8.817%   $243.5869   $243.59   $243.60   $243.60  
  Purchase #6 $8.71   8.490%   $9.4495   $9.45   $9.45   $9.40  
  Purchase #7 $249.71   4.866%   $261.8609   $261.86   $261.85   $261.90  
  7 purchase totals = $1,090.56       $1,195.1002   $1,195.11   $1,195.10   $1,195.10