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 $164.73   11.732%   $184.0561   $184.06   $184.05   $184.10  
  Purchase #2 $195.80   10.673%   $216.6977   $216.70   $216.70   $216.70  
  Purchase #3 $98.70   8.385%   $106.976   $106.98   $107.00   $107.00  
  Purchase #4 $237.74   10.196%   $261.98   $261.98   $262.00   $262.00  
  Purchase #5 $23.32   6.583%   $24.8552   $24.86   $24.85   $24.90  
  Purchase #6 $134.92   12.761%   $152.1371   $152.14   $152.15   $152.10  
  Purchase #7 $206.43   11.134%   $229.4139   $229.41   $229.40   $229.40  
  7 purchase totals = $1,061.64       $1,176.1160   $1,176.13   $1,176.15   $1,176.20