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 $108.54   9.747%   $119.1194   $119.12   $119.10   $119.10  
  Purchase #2 $195.96   4.459%   $204.6979   $204.70   $204.70   $204.70  
  Purchase #3 $14.46   6.825%   $15.4469   $15.45   $15.45   $15.40  
  Purchase #4 $230.65   12.517%   $259.5205   $259.52   $259.50   $259.50  
  Purchase #5 $38.99   5.838%   $41.2662   $41.27   $41.25   $41.30  
  Purchase #6 $120.48   4.500%   $125.9016   $125.90   $125.90   $125.90  
  Purchase #7 $55.84   5.851%   $59.1072   $59.11   $59.10   $59.10  
  7 purchase totals = $764.92       $825.0597   $825.07   $825.00   $825.00