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 $176.28   10.673%   $195.0944   $195.09   $195.10   $195.10  
  Purchase #2 $226.43   12.475%   $254.6771   $254.68   $254.70   $254.70  
  Purchase #3 $53.44   9.689%   $58.6178   $58.62   $58.60   $58.60  
  Purchase #4 $120.94   9.333%   $132.2273   $132.23   $132.25   $132.20  
  Purchase #5 $121.38   10.391%   $133.9926   $133.99   $134.00   $134.00  
  Purchase #6 $238.84   3.197%   $246.4757   $246.48   $246.50   $246.50  
  Purchase #7 $18.85   6.594%   $20.093   $20.09   $20.10   $20.10  
  7 purchase totals = $956.16       $1,041.1779   $1,041.18   $1,041.25   $1,041.20