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 $67.39   12.681%   $75.9357   $75.94   $75.95   $75.90  
  Purchase #2 $185.41   4.227%   $193.2473   $193.25   $193.25   $193.20  
  Purchase #3 $159.70   4.637%   $167.1053   $167.11   $167.10   $167.10  
  Purchase #4 $83.70   6.483%   $89.1263   $89.13   $89.15   $89.10  
  Purchase #5 $137.38   3.547%   $142.2529   $142.25   $142.25   $142.30  
  Purchase #6 $212.37   10.440%   $234.5414   $234.54   $234.55   $234.50  
  Purchase #7 $152.30   5.435%   $160.5775   $160.58   $160.60   $160.60  
  7 purchase totals = $998.25       $1,062.7864   $1,062.80   $1,062.85   $1,062.70