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 $57.40   7.744%   $61.8451   $61.85   $61.85   $61.80  
  Purchase #2 $206.25   9.254%   $225.3364   $225.34   $225.35   $225.30  
  Purchase #3 $197.78   3.757%   $205.2106   $205.21   $205.20   $205.20  
  Purchase #4 $201.98   5.303%   $212.691   $212.69   $212.70   $212.70  
  Purchase #5 $173.50   3.320%   $179.2602   $179.26   $179.25   $179.30  
  Purchase #6 $214.31   4.870%   $224.7469   $224.75   $224.75   $224.70  
  Purchase #7 $134.64   13.829%   $153.2594   $153.26   $153.25   $153.30  
  7 purchase totals = $1,185.86       $1,262.3496   $1,262.36   $1,262.35   $1,262.30