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 $182.94   6.675%   $195.1512   $195.15   $195.15   $195.20  
  Purchase #2 $54.85   5.245%   $57.7269   $57.73   $57.75   $57.70  
  Purchase #3 $125.51   7.324%   $134.7024   $134.70   $134.70   $134.70  
  Purchase #4 $87.41   10.720%   $96.7804   $96.78   $96.80   $96.80  
  Purchase #5 $93.28   10.835%   $103.3869   $103.39   $103.40   $103.40  
  Purchase #6 $121.97   7.508%   $131.1275   $131.13   $131.15   $131.10  
  Purchase #7 $119.79   11.656%   $133.7527   $133.75   $133.75   $133.80  
  7 purchase totals = $785.75       $852.6280   $852.63   $852.70   $852.70