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 $61.98   9.628%   $67.9474   $67.95   $67.95   $67.90  
  Purchase #2 $70.63   5.562%   $74.5584   $74.56   $74.55   $74.60  
  Purchase #3 $131.86   5.714%   $139.3945   $139.39   $139.40   $139.40  
  Purchase #4 $172.82   10.607%   $191.151   $191.15   $191.15   $191.20  
  Purchase #5 $210.93   11.375%   $234.9233   $234.92   $234.90   $234.90  
  Purchase #6 $169.44   3.260%   $174.9637   $174.96   $174.95   $175.00  
  Purchase #7 $63.96   5.641%   $67.568   $67.57   $67.55   $67.60  
  7 purchase totals = $881.62       $950.5063   $950.50   $950.45   $950.60