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 $190.92   7.467%   $205.176   $205.18   $205.20   $205.20  
  Purchase #2 $219.91   7.547%   $236.5066   $236.51   $236.50   $236.50  
  Purchase #3 $99.39   8.752%   $108.0886   $108.09   $108.10   $108.10  
  Purchase #4 $172.75   7.533%   $185.7633   $185.76   $185.75   $185.80  
  Purchase #5 $241.56   7.104%   $258.7204   $258.72   $258.70   $258.70  
  Purchase #6 $60.72   5.635%   $64.1416   $64.14   $64.15   $64.10  
  Purchase #7 $50.33   11.264%   $55.9992   $56.00   $56.00   $56.00  
  7 purchase totals = $1,035.58       $1,114.3957   $1,114.40   $1,114.40   $1,114.40