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 $167.46   3.854%   $173.9139   $173.91   $173.90   $173.90  
  Purchase #2 $197.42   6.612%   $210.4734   $210.47   $210.45   $210.50  
  Purchase #3 $27.55   8.737%   $29.957   $29.96   $29.95   $30.00  
  Purchase #4 $212.96   12.644%   $239.8867   $239.89   $239.90   $239.90  
  Purchase #5 $50.73   6.796%   $54.1776   $54.18   $54.20   $54.20  
  Purchase #6 $158.93   13.761%   $180.8004   $180.80   $180.80   $180.80  
  Purchase #7 $210.49   6.759%   $224.717   $224.72   $224.70   $224.70  
  7 purchase totals = $1,025.54       $1,113.9260   $1,113.93   $1,113.90   $1,114.00