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 $194.93   4.685%   $204.0625   $204.06   $204.05   $204.10  
  Purchase #2 $47.31   12.641%   $53.2905   $53.29   $53.30   $53.30  
  Purchase #3 $178.75   9.196%   $195.1879   $195.19   $195.20   $195.20  
  Purchase #4 $230.77   10.542%   $255.0978   $255.10   $255.10   $255.10  
  Purchase #5 $205.89   4.762%   $215.6945   $215.69   $215.70   $215.70  
  Purchase #6 $131.60   11.638%   $146.9156   $146.92   $146.90   $146.90  
  Purchase #7 $22.26   12.416%   $25.0238   $25.02   $25.00   $25.00  
  7 purchase totals = $1,011.51       $1,095.2726   $1,095.27   $1,095.25   $1,095.30