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 $23.76   9.340%   $25.9792   $25.98   $26.00   $26.00  
  Purchase #2 $163.94   5.703%   $173.2895   $173.29   $173.30   $173.30  
  Purchase #3 $110.82   12.225%   $124.3677   $124.37   $124.35   $124.40  
  Purchase #4 $49.61   9.240%   $54.194   $54.19   $54.20   $54.20  
  Purchase #5 $31.72   7.737%   $34.1742   $34.17   $34.15   $34.20  
  Purchase #6 $59.92   7.153%   $64.2061   $64.21   $64.20   $64.20  
  Purchase #7 $212.62   10.867%   $235.7254   $235.73   $235.75   $235.70  
  7 purchase totals = $652.39       $711.9361   $711.94   $711.95   $712.00