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 $22.49   11.629%   $25.1054   $25.11   $25.10   $25.10  
  Purchase #2 $207.91   11.311%   $231.4267   $231.43   $231.45   $231.40  
  Purchase #3 $46.89   9.504%   $51.3464   $51.35   $51.35   $51.30  
  Purchase #4 $131.74   10.548%   $145.6359   $145.64   $145.65   $145.60  
  Purchase #5 $230.80   12.680%   $260.0654   $260.07   $260.05   $260.10  
  Purchase #6 $213.51   12.844%   $240.9332   $240.93   $240.95   $240.90  
  Purchase #7 $57.50   4.207%   $59.919   $59.92   $59.90   $59.90  
  7 purchase totals = $910.84       $1,014.4320   $1,014.45   $1,014.45   $1,014.30