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 $114.62   7.482%   $123.1959   $123.20   $123.20   $123.20  
  Purchase #2 $230.63   10.540%   $254.9384   $254.94   $254.95   $254.90  
  Purchase #3 $206.39   8.837%   $224.6287   $224.63   $224.65   $224.60  
  Purchase #4 $154.89   10.453%   $171.0807   $171.08   $171.10   $171.10  
  Purchase #5 $152.99   13.578%   $173.763   $173.76   $173.75   $173.80  
  Purchase #6 $81.75   5.176%   $85.9814   $85.98   $86.00   $86.00  
  Purchase #7 $84.29   10.193%   $92.8817   $92.88   $92.90   $92.90  
  7 purchase totals = $1,025.56       $1,126.4698   $1,126.47   $1,126.55   $1,126.50