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 $93.64   9.617%   $102.6454   $102.65   $102.65   $102.60  
  Purchase #2 $190.31   8.560%   $206.6005   $206.60   $206.60   $206.60  
  Purchase #3 $217.59   10.237%   $239.8647   $239.86   $239.85   $239.90  
  Purchase #4 $191.60   12.401%   $215.3603   $215.36   $215.35   $215.40  
  Purchase #5 $211.37   5.330%   $222.636   $222.64   $222.65   $222.60  
  Purchase #6 $231.56   11.663%   $258.5668   $258.57   $258.55   $258.60  
  Purchase #7 $105.92   7.560%   $113.9276   $113.93   $113.95   $113.90  
  7 purchase totals = $1,241.99       $1,359.6013   $1,359.61   $1,359.60   $1,359.60