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 $216.79   9.623%   $237.6517   $237.65   $237.65   $237.70  
  Purchase #2 $169.75   9.199%   $185.3653   $185.37   $185.35   $185.40  
  Purchase #3 $246.33   12.513%   $277.1533   $277.15   $277.15   $277.20  
  Purchase #4 $151.25   10.446%   $167.0496   $167.05   $167.05   $167.00  
  Purchase #5 $163.62   10.466%   $180.7445   $180.74   $180.75   $180.70  
  Purchase #6 $72.86   7.557%   $78.366   $78.37   $78.35   $78.40  
  Purchase #7 $134.33   8.827%   $146.1873   $146.19   $146.20   $146.20  
  7 purchase totals = $1,154.93       $1,272.5177   $1,272.52   $1,272.50   $1,272.60