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 $79.58   9.651%   $87.2603   $87.26   $87.25   $87.30  
  Purchase #2 $208.56   3.358%   $215.5634   $215.56   $215.55   $215.60  
  Purchase #3 $71.94   4.766%   $75.3687   $75.37   $75.35   $75.40  
  Purchase #4 $231.57   5.655%   $244.6653   $244.67   $244.65   $244.70  
  Purchase #5 $188.25   12.618%   $212.0034   $212.00   $212.00   $212.00  
  Purchase #6 $95.88   13.853%   $109.1623   $109.16   $109.15   $109.20  
  Purchase #7 $139.87   13.850%   $159.242   $159.24   $159.25   $159.20  
  7 purchase totals = $1,015.65       $1,103.2654   $1,103.26   $1,103.20   $1,103.40