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 $59.85   10.152%   $65.926   $65.93   $65.95   $65.90  
  Purchase #2 $242.72   8.149%   $262.4993   $262.50   $262.50   $262.50  
  Purchase #3 $104.99   9.547%   $115.0134   $115.01   $115.00   $115.00  
  Purchase #4 $79.71   7.818%   $85.9417   $85.94   $85.95   $85.90  
  Purchase #5 $24.62   11.743%   $27.5111   $27.51   $27.50   $27.50  
  Purchase #6 $88.74   5.409%   $93.5399   $93.54   $93.55   $93.50  
  Purchase #7 $203.72   7.386%   $218.7668   $218.77   $218.75   $218.80  
  7 purchase totals = $804.35       $869.1982   $869.20   $869.20   $869.10