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 $203.44   4.722%   $213.0464   $213.05   $213.05   $213.00  
  Purchase #2 $242.97   13.332%   $275.3628   $275.36   $275.35   $275.40  
  Purchase #3 $35.31   11.330%   $39.3106   $39.31   $39.30   $39.30  
  Purchase #4 $250.64   12.666%   $282.3861   $282.39   $282.40   $282.40  
  Purchase #5 $129.27   6.134%   $137.1994   $137.20   $137.20   $137.20  
  Purchase #6 $135.57   8.644%   $147.2887   $147.29   $147.30   $147.30  
  Purchase #7 $16.86   4.505%   $17.6195   $17.62   $17.60   $17.60  
  7 purchase totals = $1,014.06       $1,112.2135   $1,112.22   $1,112.20   $1,112.20