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 $167.52   11.150%   $186.1985   $186.20   $186.20   $186.20  
  Purchase #2 $86.93   10.412%   $95.9812   $95.98   $96.00   $96.00  
  Purchase #3 $45.54   8.728%   $49.5147   $49.51   $49.50   $49.50  
  Purchase #4 $175.56   10.295%   $193.6339   $193.63   $193.65   $193.60  
  Purchase #5 $215.37   13.631%   $244.7271   $244.73   $244.75   $244.70  
  Purchase #6 $40.35   3.872%   $41.9124   $41.91   $41.90   $41.90  
  Purchase #7 $99.77   13.263%   $113.0025   $113.00   $113.00   $113.00  
  7 purchase totals = $831.04       $924.9703   $924.96   $925.00   $924.90