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 $194.78   3.416%   $201.4337   $201.43   $201.45   $201.40  
  Purchase #2 $33.71   10.119%   $37.1211   $37.12   $37.10   $37.10  
  Purchase #3 $235.46   3.541%   $243.7976   $243.80   $243.80   $243.80  
  Purchase #4 $41.85   4.321%   $43.6583   $43.66   $43.65   $43.70  
  Purchase #5 $85.81   6.604%   $91.4769   $91.48   $91.50   $91.50  
  Purchase #6 $179.55   8.635%   $195.0541   $195.05   $195.05   $195.10  
  Purchase #7 $58.42   7.271%   $62.6677   $62.67   $62.65   $62.70  
  7 purchase totals = $829.58       $875.2094   $875.21   $875.20   $875.30