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 $182.48   4.751%   $191.1496   $191.15   $191.15   $191.10  
  Purchase #2 $112.28   10.308%   $123.8538   $123.85   $123.85   $123.90  
  Purchase #3 $180.49   12.786%   $203.5675   $203.57   $203.55   $203.60  
  Purchase #4 $190.87   11.482%   $212.7857   $212.79   $212.80   $212.80  
  Purchase #5 $196.35   10.541%   $217.0473   $217.05   $217.05   $217.00  
  Purchase #6 $20.71   5.123%   $21.771   $21.77   $21.75   $21.80  
  Purchase #7 $130.80   4.584%   $136.7959   $136.80   $136.80   $136.80  
  7 purchase totals = $1,013.98       $1,106.9708   $1,106.98   $1,106.95   $1,107.00