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 $64.53   8.223%   $69.8363   $69.84   $69.85   $69.80  
  Purchase #2 $190.38   8.743%   $207.0249   $207.02   $207.00   $207.00  
  Purchase #3 $246.41   8.402%   $267.1134   $267.11   $267.10   $267.10  
  Purchase #4 $191.34   7.502%   $205.6943   $205.69   $205.70   $205.70  
  Purchase #5 $28.89   4.856%   $30.2929   $30.29   $30.30   $30.30  
  Purchase #6 $108.47   10.173%   $119.5047   $119.50   $119.50   $119.50  
  Purchase #7 $206.49   4.226%   $215.2163   $215.22   $215.20   $215.20  
  7 purchase totals = $1,036.51       $1,114.6828   $1,114.67   $1,114.65   $1,114.60