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 $34.91   6.114%   $37.0444   $37.04   $37.05   $37.00  
  Purchase #2 $81.87   12.738%   $92.2986   $92.30   $92.30   $92.30  
  Purchase #3 $74.40   3.339%   $76.8842   $76.88   $76.90   $76.90  
  Purchase #4 $69.75   3.175%   $71.9646   $71.96   $71.95   $72.00  
  Purchase #5 $201.86   11.703%   $225.4837   $225.48   $225.50   $225.50  
  Purchase #6 $233.78   13.745%   $265.9131   $265.91   $265.90   $265.90  
  Purchase #7 $109.54   6.564%   $116.7302   $116.73   $116.75   $116.70  
  7 purchase totals = $806.11       $886.3188   $886.30   $886.35   $886.30