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 $211.43   6.527%   $225.23   $225.23   $225.25   $225.20  
  Purchase #2 $71.67   7.335%   $76.927   $76.93   $76.95   $76.90  
  Purchase #3 $168.58   12.278%   $189.2783   $189.28   $189.30   $189.30  
  Purchase #4 $120.49   4.290%   $125.659   $125.66   $125.65   $125.70  
  Purchase #5 $115.58   6.401%   $122.9783   $122.98   $123.00   $123.00  
  Purchase #6 $179.56   3.517%   $185.8751   $185.88   $185.90   $185.90  
  Purchase #7 $107.94   10.269%   $119.0244   $119.02   $119.00   $119.00  
  7 purchase totals = $975.25       $1,044.9721   $1,044.98   $1,045.05   $1,045.00