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 $39.46   6.302%   $41.9468   $41.95   $41.95   $41.90  
  Purchase #2 $233.70   10.794%   $258.9256   $258.93   $258.95   $258.90  
  Purchase #3 $97.32   8.781%   $105.8657   $105.87   $105.85   $105.90  
  Purchase #4 $247.96   9.655%   $271.9005   $271.90   $271.90   $271.90  
  Purchase #5 $147.76   13.472%   $167.6662   $167.67   $167.65   $167.70  
  Purchase #6 $165.42   5.533%   $174.5727   $174.57   $174.55   $174.60  
  Purchase #7 $173.92   11.421%   $193.7834   $193.78   $193.80   $193.80  
  7 purchase totals = $1,105.54       $1,214.6609   $1,214.67   $1,214.65   $1,214.70