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 $95.82   11.595%   $106.9303   $106.93   $106.95   $106.90  
  Purchase #2 $245.35   5.110%   $257.8874   $257.89   $257.90   $257.90  
  Purchase #3 $127.81   5.248%   $134.5175   $134.52   $134.50   $134.50  
  Purchase #4 $229.83   9.310%   $251.2272   $251.23   $251.25   $251.20  
  Purchase #5 $194.50   8.242%   $210.5307   $210.53   $210.55   $210.50  
  Purchase #6 $62.52   6.368%   $66.5013   $66.50   $66.50   $66.50  
  Purchase #7 $113.68   10.341%   $125.4356   $125.44   $125.45   $125.40  
  7 purchase totals = $1,069.51       $1,153.0300   $1,153.04   $1,153.10   $1,152.90