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 $195.77   9.740%   $214.838   $214.84   $214.85   $214.80  
  Purchase #2 $177.56   13.747%   $201.9692   $201.97   $201.95   $202.00  
  Purchase #3 $99.73   3.774%   $103.4938   $103.49   $103.50   $103.50  
  Purchase #4 $89.44   13.558%   $101.5663   $101.57   $101.55   $101.60  
  Purchase #5 $142.28   9.539%   $155.8521   $155.85   $155.85   $155.90  
  Purchase #6 $39.38   6.299%   $41.8605   $41.86   $41.85   $41.90  
  Purchase #7 $205.61   13.601%   $233.575   $233.58   $233.60   $233.60  
  7 purchase totals = $949.77       $1,053.1549   $1,053.16   $1,053.15   $1,053.30