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 $87.78   8.781%   $95.488   $95.49   $95.50   $95.50  
  Purchase #2 $240.75   11.161%   $267.6201   $267.62   $267.60   $267.60  
  Purchase #3 $140.29   3.468%   $145.1553   $145.16   $145.15   $145.20  
  Purchase #4 $246.85   8.695%   $268.3136   $268.31   $268.30   $268.30  
  Purchase #5 $83.97   9.860%   $92.2494   $92.25   $92.25   $92.20  
  Purchase #6 $234.50   6.563%   $249.8902   $249.89   $249.90   $249.90  
  Purchase #7 $224.29   12.643%   $252.647   $252.65   $252.65   $252.60  
  7 purchase totals = $1,258.43       $1,371.3636   $1,371.37   $1,371.35   $1,371.30