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 $208.53   8.763%   $226.8035   $226.80   $226.80   $226.80  
  Purchase #2 $197.50   7.809%   $212.9228   $212.92   $212.90   $212.90  
  Purchase #3 $57.30   8.532%   $62.1888   $62.19   $62.20   $62.20  
  Purchase #4 $111.74   6.385%   $118.8746   $118.87   $118.85   $118.90  
  Purchase #5 $117.40   13.250%   $132.9555   $132.96   $132.95   $133.00  
  Purchase #6 $174.37   7.661%   $187.7285   $187.73   $187.75   $187.70  
  Purchase #7 $79.36   6.710%   $84.6851   $84.69   $84.70   $84.70  
  7 purchase totals = $946.20       $1,026.1588   $1,026.16   $1,026.15   $1,026.20