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 $84.28   12.413%   $94.7417   $94.74   $94.75   $94.70  
  Purchase #2 $139.36   12.500%   $156.78   $156.78   $156.80   $156.80  
  Purchase #3 $61.89   8.373%   $67.072   $67.07   $67.05   $67.10  
  Purchase #4 $161.64   5.340%   $170.2716   $170.27   $170.25   $170.30  
  Purchase #5 $196.40   5.625%   $207.4475   $207.45   $207.45   $207.40  
  Purchase #6 $13.90   4.806%   $14.568   $14.57   $14.55   $14.60  
  Purchase #7 $223.93   4.708%   $234.4726   $234.47   $234.45   $234.50  
  7 purchase totals = $881.40       $945.3534   $945.35   $945.30   $945.40