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 $83.62   10.266%   $92.2044   $92.20   $92.20   $92.20  
  Purchase #2 $229.89   6.822%   $245.5731   $245.57   $245.55   $245.60  
  Purchase #3 $48.37   6.351%   $51.442   $51.44   $51.45   $51.40  
  Purchase #4 $140.56   11.316%   $156.4658   $156.47   $156.45   $156.50  
  Purchase #5 $207.57   8.540%   $225.2965   $225.30   $225.30   $225.30  
  Purchase #6 $234.35   5.314%   $246.8034   $246.80   $246.80   $246.80  
  Purchase #7 $33.80   9.204%   $36.911   $36.91   $36.90   $36.90  
  7 purchase totals = $978.16       $1,054.6962   $1,054.69   $1,054.65   $1,054.70