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 $71.53   6.269%   $76.0142   $76.01   $76.00   $76.00  
  Purchase #2 $130.38   5.140%   $137.0815   $137.08   $137.10   $137.10  
  Purchase #3 $247.55   6.502%   $263.6457   $263.65   $263.65   $263.60  
  Purchase #4 $175.48   11.359%   $195.4128   $195.41   $195.40   $195.40  
  Purchase #5 $238.53   7.783%   $257.0948   $257.09   $257.10   $257.10  
  Purchase #6 $32.39   3.162%   $33.4142   $33.41   $33.40   $33.40  
  Purchase #7 $118.55   11.266%   $131.9058   $131.91   $131.90   $131.90  
  7 purchase totals = $1,014.41       $1,094.5690   $1,094.56   $1,094.55   $1,094.50