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 $56.57   10.707%   $62.6269   $62.63   $62.65   $62.60  
  Purchase #2 $137.26   10.464%   $151.6229   $151.62   $151.60   $151.60  
  Purchase #3 $194.66   12.311%   $218.6246   $218.62   $218.60   $218.60  
  Purchase #4 $235.96   9.503%   $258.3833   $258.38   $258.40   $258.40  
  Purchase #5 $241.90   13.130%   $273.6615   $273.66   $273.65   $273.70  
  Purchase #6 $24.59   8.283%   $26.6268   $26.63   $26.65   $26.60  
  Purchase #7 $70.38   9.185%   $76.8444   $76.84   $76.85   $76.80  
  7 purchase totals = $961.32       $1,068.3904   $1,068.38   $1,068.40   $1,068.30