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 $56.52   8.333%   $61.2298   $61.23   $61.25   $61.20  
  Purchase #2 $239.30   12.279%   $268.6836   $268.68   $268.70   $268.70  
  Purchase #3 $236.32   8.395%   $256.1591   $256.16   $256.15   $256.20  
  Purchase #4 $34.31   7.579%   $36.9104   $36.91   $36.90   $36.90  
  Purchase #5 $205.43   3.785%   $213.2055   $213.21   $213.20   $213.20  
  Purchase #6 $29.75   4.525%   $31.0962   $31.10   $31.10   $31.10  
  Purchase #7 $224.99   6.199%   $238.9371   $238.94   $238.95   $238.90  
  7 purchase totals = $1,026.62       $1,106.2217   $1,106.23   $1,106.25   $1,106.20