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 $114.60   7.286%   $122.9498   $122.95   $122.95   $122.90  
  Purchase #2 $29.90   10.302%   $32.9803   $32.98   $33.00   $33.00  
  Purchase #3 $76.94   9.254%   $84.06   $84.06   $84.05   $84.10  
  Purchase #4 $95.73   7.299%   $102.7173   $102.72   $102.70   $102.70  
  Purchase #5 $7.25   10.641%   $8.0215   $8.02   $8.00   $8.00  
  Purchase #6 $141.29   8.514%   $153.3194   $153.32   $153.30   $153.30  
  Purchase #7 $234.55   10.775%   $259.8228   $259.82   $259.80   $259.80  
  7 purchase totals = $700.26       $763.8711   $763.87   $763.80   $763.80