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 $119.80   10.789%   $132.7252   $132.73   $132.75   $132.70  
  Purchase #2 $86.42   10.219%   $95.2513   $95.25   $95.25   $95.30  
  Purchase #3 $117.93   13.411%   $133.7456   $133.75   $133.75   $133.70  
  Purchase #4 $247.59   3.608%   $256.523   $256.52   $256.50   $256.50  
  Purchase #5 $102.85   4.197%   $107.1666   $107.17   $107.15   $107.20  
  Purchase #6 $114.79   3.445%   $118.7445   $118.74   $118.75   $118.70  
  Purchase #7 $163.72   11.571%   $182.664   $182.66   $182.65   $182.70  
  7 purchase totals = $953.10       $1,026.8202   $1,026.82   $1,026.80   $1,026.80