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 $242.38   8.187%   $262.2237   $262.22   $262.20   $262.20  
  Purchase #2 $85.68   12.580%   $96.4585   $96.46   $96.45   $96.50  
  Purchase #3 $100.73   10.638%   $111.4457   $111.45   $111.45   $111.40  
  Purchase #4 $20.70   5.199%   $21.7762   $21.78   $21.80   $21.80  
  Purchase #5 $31.73   13.737%   $36.0888   $36.09   $36.10   $36.10  
  Purchase #6 $209.67   12.437%   $235.7467   $235.75   $235.75   $235.70  
  Purchase #7 $236.69   6.115%   $251.1636   $251.16   $251.15   $251.20  
  7 purchase totals = $927.58       $1,014.9032   $1,014.91   $1,014.90   $1,014.90