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 $205.51   4.764%   $215.3005   $215.30   $215.30   $215.30  
  Purchase #2 $185.91   6.474%   $197.9458   $197.95   $197.95   $197.90  
  Purchase #3 $100.26   6.357%   $106.6335   $106.63   $106.65   $106.60  
  Purchase #4 $16.61   4.505%   $17.3583   $17.36   $17.35   $17.40  
  Purchase #5 $125.44   4.354%   $130.9017   $130.90   $130.90   $130.90  
  Purchase #6 $179.70   10.844%   $199.1867   $199.19   $199.20   $199.20  
  Purchase #7 $237.30   3.477%   $245.5509   $245.55   $245.55   $245.60  
  7 purchase totals = $1,050.73       $1,112.8774   $1,112.88   $1,112.90   $1,112.90