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 $42.91   9.487%   $46.9809   $46.98   $47.00   $47.00  
  Purchase #2 $242.36   8.278%   $262.4226   $262.42   $262.40   $262.40  
  Purchase #3 $148.80   11.526%   $165.9507   $165.95   $165.95   $166.00  
  Purchase #4 $246.99   11.710%   $275.9125   $275.91   $275.90   $275.90  
  Purchase #5 $70.27   5.793%   $74.3407   $74.34   $74.35   $74.30  
  Purchase #6 $89.34   5.429%   $94.1903   $94.19   $94.20   $94.20  
  Purchase #7 $134.39   8.635%   $145.9946   $145.99   $146.00   $146.00  
  7 purchase totals = $975.06       $1,065.7923   $1,065.78   $1,065.80   $1,065.80