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 $213.37   10.300%   $235.3471   $235.35   $235.35   $235.30  
  Purchase #2 $74.89   13.596%   $85.072   $85.07   $85.05   $85.10  
  Purchase #3 $130.77   4.667%   $136.873   $136.87   $136.85   $136.90  
  Purchase #4 $84.38   11.228%   $93.8542   $93.85   $93.85   $93.90  
  Purchase #5 $177.44   10.369%   $195.8388   $195.84   $195.85   $195.80  
  Purchase #6 $172.46   7.307%   $185.0617   $185.06   $185.05   $185.10  
  Purchase #7 $86.56   8.648%   $94.0457   $94.05   $94.05   $94.00  
  7 purchase totals = $939.87       $1,026.0925   $1,026.09   $1,026.05   $1,026.10