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 $175.87   3.649%   $182.2875   $182.29   $182.30   $182.30  
  Purchase #2 $47.92   8.532%   $52.0085   $52.01   $52.00   $52.00  
  Purchase #3 $139.32   13.155%   $157.6475   $157.65   $157.65   $157.60  
  Purchase #4 $204.70   9.806%   $224.7729   $224.77   $224.75   $224.80  
  Purchase #5 $117.63   6.360%   $125.1113   $125.11   $125.10   $125.10  
  Purchase #6 $216.47   8.372%   $234.5929   $234.59   $234.60   $234.60  
  Purchase #7 $114.39   4.247%   $119.2481   $119.25   $119.25   $119.20  
  7 purchase totals = $1,016.30       $1,095.6687   $1,095.67   $1,095.65   $1,095.60