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 $116.35   8.825%   $126.6179   $126.62   $126.60   $126.60  
  Purchase #2 $235.58   9.634%   $258.2758   $258.28   $258.30   $258.30  
  Purchase #3 $246.77   12.528%   $277.6853   $277.69   $277.70   $277.70  
  Purchase #4 $14.42   9.424%   $15.7789   $15.78   $15.80   $15.80  
  Purchase #5 $156.63   12.537%   $176.2667   $176.27   $176.25   $176.30  
  Purchase #6 $87.95   6.419%   $93.5955   $93.60   $93.60   $93.60  
  Purchase #7 $205.92   3.835%   $213.817   $213.82   $213.80   $213.80  
  7 purchase totals = $1,063.62       $1,162.0371   $1,162.06   $1,162.05   $1,162.10