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 $61.84   6.321%   $65.7489   $65.75   $65.75   $65.70  
  Purchase #2 $209.96   7.315%   $225.3186   $225.32   $225.30   $225.30  
  Purchase #3 $70.33   4.699%   $73.6348   $73.63   $73.65   $73.60  
  Purchase #4 $222.89   4.107%   $232.0441   $232.04   $232.05   $232.00  
  Purchase #5 $203.34   7.371%   $218.3282   $218.33   $218.35   $218.30  
  Purchase #6 $76.45   12.450%   $85.968   $85.97   $85.95   $86.00  
  Purchase #7 $158.37   5.298%   $166.7604   $166.76   $166.75   $166.80  
  7 purchase totals = $1,003.18       $1,067.8030   $1,067.80   $1,067.80   $1,067.70