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 $218.54   6.843%   $233.4947   $233.49   $233.50   $233.50  
  Purchase #2 $162.68   13.268%   $184.2644   $184.26   $184.25   $184.30  
  Purchase #3 $246.41   8.680%   $267.7984   $267.80   $267.80   $267.80  
  Purchase #4 $103.70   8.548%   $112.5643   $112.56   $112.55   $112.60  
  Purchase #5 $154.33   7.427%   $165.7921   $165.79   $165.80   $165.80  
  Purchase #6 $10.32   12.364%   $11.596   $11.60   $11.60   $11.60  
  Purchase #7 $120.38   11.813%   $134.6005   $134.60   $134.60   $134.60  
  7 purchase totals = $1,016.36       $1,110.1104   $1,110.10   $1,110.10   $1,110.20