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 $244.62   9.214%   $267.1593   $267.16   $267.15   $267.20  
  Purchase #2 $197.74   13.833%   $225.0934   $225.09   $225.10   $225.10  
  Purchase #3 $23.47   8.758%   $25.5255   $25.53   $25.55   $25.50  
  Purchase #4 $79.57   12.514%   $89.5274   $89.53   $89.55   $89.50  
  Purchase #5 $118.51   5.635%   $125.188   $125.19   $125.20   $125.20  
  Purchase #6 $240.37   11.352%   $267.6568   $267.66   $267.65   $267.70  
  Purchase #7 $180.90   8.231%   $195.7899   $195.79   $195.80   $195.80  
  7 purchase totals = $1,085.18       $1,195.9403   $1,195.95   $1,196.00   $1,196.00