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 $44.44   7.567%   $47.8028   $47.80   $47.80   $47.80  
  Purchase #2 $158.87   6.560%   $169.2919   $169.29   $169.30   $169.30  
  Purchase #3 $25.92   4.498%   $27.0859   $27.09   $27.10   $27.10  
  Purchase #4 $218.89   8.431%   $237.3446   $237.34   $237.35   $237.30  
  Purchase #5 $229.69   9.278%   $251.0006   $251.00   $251.00   $251.00  
  Purchase #6 $168.60   9.649%   $184.8682   $184.87   $184.85   $184.90  
  Purchase #7 $183.72   9.709%   $201.5574   $201.56   $201.55   $201.60  
  7 purchase totals = $1,030.13       $1,118.9514   $1,118.95   $1,118.95   $1,119.00