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 $86.93   6.303%   $92.4092   $92.41   $92.40   $92.40  
  Purchase #2 $227.37   11.529%   $253.5835   $253.58   $253.60   $253.60  
  Purchase #3 $127.28   11.369%   $141.7505   $141.75   $141.75   $141.80  
  Purchase #4 $197.71   3.179%   $203.9952   $204.00   $204.00   $204.00  
  Purchase #5 $161.51   11.182%   $179.57   $179.57   $179.55   $179.60  
  Purchase #6 $101.39   6.756%   $108.2399   $108.24   $108.25   $108.20  
  Purchase #7 $75.91   7.119%   $81.314   $81.31   $81.30   $81.30  
  7 purchase totals = $978.10       $1,060.8623   $1,060.86   $1,060.85   $1,060.90