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 $43.64   5.849%   $46.1925   $46.19   $46.20   $46.20  
  Purchase #2 $233.64   13.113%   $264.2772   $264.28   $264.30   $264.30  
  Purchase #3 $126.50   4.410%   $132.0787   $132.08   $132.10   $132.10  
  Purchase #4 $219.49   12.443%   $246.8011   $246.80   $246.80   $246.80  
  Purchase #5 $165.39   8.533%   $179.5027   $179.50   $179.50   $179.50  
  Purchase #6 $225.77   7.463%   $242.6192   $242.62   $242.60   $242.60  
  Purchase #7 $231.95   11.357%   $258.2926   $258.29   $258.30   $258.30  
  7 purchase totals = $1,246.38       $1,369.7640   $1,369.76   $1,369.80   $1,369.80