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 $60.95   10.473%   $67.3333   $67.33   $67.35   $67.30  
  Purchase #2 $159.29   12.701%   $179.5214   $179.52   $179.50   $179.50  
  Purchase #3 $31.36   9.131%   $34.2235   $34.22   $34.20   $34.20  
  Purchase #4 $10.92   8.215%   $11.8171   $11.82   $11.80   $11.80  
  Purchase #5 $134.52   7.578%   $144.7139   $144.71   $144.70   $144.70  
  Purchase #6 $240.63   12.306%   $270.2419   $270.24   $270.25   $270.20  
  Purchase #7 $224.46   12.746%   $253.0697   $253.07   $253.05   $253.10  
  7 purchase totals = $862.13       $960.9208   $960.91   $960.85   $960.80