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 $209.58   7.369%   $225.024   $225.02   $225.00   $225.00  
  Purchase #2 $111.39   7.514%   $119.7598   $119.76   $119.75   $119.80  
  Purchase #3 $224.64   12.320%   $252.3156   $252.32   $252.30   $252.30  
  Purchase #4 $150.62   12.397%   $169.2924   $169.29   $169.30   $169.30  
  Purchase #5 $212.37   12.704%   $239.3495   $239.35   $239.35   $239.30  
  Purchase #6 $25.67   8.473%   $27.845   $27.85   $27.85   $27.80  
  Purchase #7 $72.97   10.158%   $80.3823   $80.38   $80.40   $80.40  
  7 purchase totals = $1,007.24       $1,113.9686   $1,113.97   $1,113.95   $1,113.90