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 $84.39   13.703%   $95.954   $95.95   $95.95   $96.00  
  Purchase #2 $83.49   5.324%   $87.935   $87.94   $87.95   $87.90  
  Purchase #3 $83.56   6.434%   $88.9363   $88.94   $88.95   $88.90  
  Purchase #4 $122.91   3.398%   $127.0865   $127.09   $127.10   $127.10  
  Purchase #5 $120.99   12.370%   $135.9565   $135.96   $135.95   $136.00  
  Purchase #6 $159.86   8.554%   $173.5344   $173.53   $173.55   $173.50  
  Purchase #7 $66.57   12.262%   $74.7328   $74.73   $74.75   $74.70  
  7 purchase totals = $721.77       $784.1355   $784.14   $784.20   $784.10