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 $213.68   5.764%   $225.9965   $226.00   $226.00   $226.00  
  Purchase #2 $231.70   12.868%   $261.5152   $261.52   $261.50   $261.50  
  Purchase #3 $168.51   3.390%   $174.2225   $174.22   $174.20   $174.20  
  Purchase #4 $60.76   7.543%   $65.3431   $65.34   $65.35   $65.30  
  Purchase #5 $13.39   9.442%   $14.6543   $14.65   $14.65   $14.70  
  Purchase #6 $172.31   4.255%   $179.6418   $179.64   $179.65   $179.60  
  Purchase #7 $88.75   3.644%   $91.9841   $91.98   $92.00   $92.00  
  7 purchase totals = $949.10       $1,013.3575   $1,013.35   $1,013.35   $1,013.30