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 $94.65   7.771%   $102.0053   $102.01   $102.00   $102.00  
  Purchase #2 $178.70   7.106%   $191.3984   $191.40   $191.40   $191.40  
  Purchase #3 $46.94   10.766%   $51.9936   $51.99   $52.00   $52.00  
  Purchase #4 $104.73   5.218%   $110.1948   $110.19   $110.20   $110.20  
  Purchase #5 $233.87   5.486%   $246.7001   $246.70   $246.70   $246.70  
  Purchase #6 $82.64   10.759%   $91.5312   $91.53   $91.55   $91.50  
  Purchase #7 $52.66   6.344%   $56.0008   $56.00   $56.00   $56.00  
  7 purchase totals = $794.19       $849.8242   $849.82   $849.85   $849.80