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 $86.79   9.511%   $95.0446   $95.04   $95.05   $95.00  
  Purchase #2 $184.96   6.776%   $197.4929   $197.49   $197.50   $197.50  
  Purchase #3 $244.93   6.146%   $259.9834   $259.98   $260.00   $260.00  
  Purchase #4 $158.86   3.868%   $165.0047   $165.00   $165.00   $165.00  
  Purchase #5 $235.51   8.129%   $254.6546   $254.65   $254.65   $254.70  
  Purchase #6 $224.58   8.830%   $244.4104   $244.41   $244.40   $244.40  
  Purchase #7 $151.41   8.503%   $164.2844   $164.28   $164.30   $164.30  
  7 purchase totals = $1,287.04       $1,380.8750   $1,380.85   $1,380.90   $1,380.90