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 $136.62   10.543%   $151.0238   $151.02   $151.00   $151.00  
  Purchase #2 $173.29   7.491%   $186.2712   $186.27   $186.25   $186.30  
  Purchase #3 $178.89   9.435%   $195.7683   $195.77   $195.75   $195.80  
  Purchase #4 $130.92   3.279%   $135.2129   $135.21   $135.20   $135.20  
  Purchase #5 $78.51   9.103%   $85.6568   $85.66   $85.65   $85.70  
  Purchase #6 $135.74   7.704%   $146.1974   $146.20   $146.20   $146.20  
  Purchase #7 $188.88   3.328%   $195.1659   $195.17   $195.15   $195.20  
  7 purchase totals = $1,022.85       $1,095.2963   $1,095.30   $1,095.20   $1,095.40