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 $74.59   3.219%   $76.9911   $76.99   $77.00   $77.00  
  Purchase #2 $178.66   8.681%   $194.1695   $194.17   $194.15   $194.20  
  Purchase #3 $81.88   4.770%   $85.7857   $85.79   $85.80   $85.80  
  Purchase #4 $231.52   6.545%   $246.673   $246.67   $246.65   $246.70  
  Purchase #5 $148.63   4.744%   $155.681   $155.68   $155.70   $155.70  
  Purchase #6 $6.42   8.152%   $6.9434   $6.94   $6.95   $6.90  
  Purchase #7 $233.62   9.666%   $256.2017   $256.20   $256.20   $256.20  
  7 purchase totals = $955.32       $1,022.4454   $1,022.44   $1,022.45   $1,022.50