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 $95.32   11.229%   $106.0235   $106.02   $106.00   $106.00  
  Purchase #2 $221.86   8.475%   $240.6626   $240.66   $240.65   $240.70  
  Purchase #3 $124.73   13.214%   $141.2118   $141.21   $141.20   $141.20  
  Purchase #4 $84.84   11.566%   $94.6526   $94.65   $94.65   $94.70  
  Purchase #5 $233.94   5.568%   $246.9658   $246.97   $246.95   $247.00  
  Purchase #6 $205.26   8.643%   $223.0006   $223.00   $223.00   $223.00  
  Purchase #7 $104.69   7.208%   $112.2361   $112.24   $112.25   $112.20  
  7 purchase totals = $1,070.64       $1,164.7530   $1,164.75   $1,164.70   $1,164.80