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 $117.82   7.642%   $126.8238   $126.82   $126.80   $126.80  
  Purchase #2 $200.42   5.803%   $212.0504   $212.05   $212.05   $212.10  
  Purchase #3 $112.30   5.757%   $118.7651   $118.77   $118.75   $118.80  
  Purchase #4 $96.31   10.453%   $106.3773   $106.38   $106.40   $106.40  
  Purchase #5 $56.44   13.793%   $64.2248   $64.22   $64.20   $64.20  
  Purchase #6 $230.50   13.304%   $261.1657   $261.17   $261.15   $261.20  
  Purchase #7 $96.50   10.148%   $106.2928   $106.29   $106.30   $106.30  
  7 purchase totals = $910.29       $995.6999   $995.70   $995.65   $995.80