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 $189.26   3.522%   $195.9257   $195.93   $195.95   $195.90  
  Purchase #2 $233.61   11.375%   $260.1831   $260.18   $260.20   $260.20  
  Purchase #3 $60.38   11.290%   $67.1969   $67.20   $67.20   $67.20  
  Purchase #4 $57.36   9.285%   $62.6859   $62.69   $62.70   $62.70  
  Purchase #5 $139.58   6.504%   $148.6583   $148.66   $148.65   $148.70  
  Purchase #6 $70.47   11.601%   $78.6452   $78.65   $78.65   $78.60  
  Purchase #7 $191.51   6.277%   $203.5311   $203.53   $203.55   $203.50  
  7 purchase totals = $942.17       $1,016.8262   $1,016.84   $1,016.90   $1,016.80