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 $196.38   5.220%   $206.631   $206.63   $206.65   $206.60  
  Purchase #2 $129.26   5.204%   $135.9867   $135.99   $136.00   $136.00  
  Purchase #3 $58.78   6.301%   $62.4837   $62.48   $62.50   $62.50  
  Purchase #4 $166.56   4.529%   $174.1035   $174.10   $174.10   $174.10  
  Purchase #5 $187.65   6.372%   $199.6071   $199.61   $199.60   $199.60  
  Purchase #6 $21.65   12.593%   $24.3764   $24.38   $24.40   $24.40  
  Purchase #7 $68.32   5.801%   $72.2832   $72.28   $72.30   $72.30  
  7 purchase totals = $828.60       $875.4716   $875.47   $875.55   $875.50