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 $83.83   13.356%   $95.0263   $95.03   $95.05   $95.00  
  Purchase #2 $208.75   7.865%   $225.1682   $225.17   $225.15   $225.20  
  Purchase #3 $197.32   6.468%   $210.0827   $210.08   $210.10   $210.10  
  Purchase #4 $22.70   13.283%   $25.7152   $25.72   $25.70   $25.70  
  Purchase #5 $142.74   5.570%   $150.6906   $150.69   $150.70   $150.70  
  Purchase #6 $197.73   5.227%   $208.0653   $208.07   $208.05   $208.10  
  Purchase #7 $55.27   3.772%   $57.3548   $57.35   $57.35   $57.40  
  7 purchase totals = $908.34       $972.1031   $972.11   $972.10   $972.20