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 $41.26   13.818%   $46.9613   $46.96   $46.95   $47.00  
  Purchase #2 $186.29   10.464%   $205.7834   $205.78   $205.80   $205.80  
  Purchase #3 $186.67   3.526%   $193.252   $193.25   $193.25   $193.30  
  Purchase #4 $118.90   3.265%   $122.7821   $122.78   $122.80   $122.80  
  Purchase #5 $204.55   10.470%   $225.9664   $225.97   $225.95   $226.00  
  Purchase #6 $219.25   11.687%   $244.8737   $244.87   $244.85   $244.90  
  Purchase #7 $116.80   7.597%   $125.6733   $125.67   $125.65   $125.70  
  7 purchase totals = $1,073.72       $1,165.2922   $1,165.28   $1,165.25   $1,165.50