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 $93.58   3.567%   $96.918   $96.92   $96.90   $96.90  
  Purchase #2 $118.90   6.351%   $126.4513   $126.45   $126.45   $126.50  
  Purchase #3 $49.95   6.473%   $53.1833   $53.18   $53.20   $53.20  
  Purchase #4 $41.35   12.537%   $46.534   $46.53   $46.55   $46.50  
  Purchase #5 $140.53   13.691%   $159.77   $159.77   $159.75   $159.80  
  Purchase #6 $29.26   12.368%   $32.8789   $32.88   $32.90   $32.90  
  Purchase #7 $111.71   7.319%   $119.8861   $119.89   $119.90   $119.90  
  7 purchase totals = $585.28       $635.6216   $635.62   $635.65   $635.70