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 $56.93   8.854%   $61.9706   $61.97   $61.95   $62.00  
  Purchase #2 $81.72   6.662%   $87.1642   $87.16   $87.15   $87.20  
  Purchase #3 $241.98   7.625%   $260.431   $260.43   $260.45   $260.40  
  Purchase #4 $157.25   9.365%   $171.9765   $171.98   $172.00   $172.00  
  Purchase #5 $246.72   3.195%   $254.6027   $254.60   $254.60   $254.60  
  Purchase #6 $208.53   3.760%   $216.3707   $216.37   $216.35   $216.40  
  Purchase #7 $250.99   11.801%   $280.6093   $280.61   $280.60   $280.60  
  7 purchase totals = $1,244.12       $1,333.1250   $1,333.12   $1,333.10   $1,333.20