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 $78.44   9.650%   $86.0095   $86.01   $86.00   $86.00  
  Purchase #2 $168.58   3.651%   $174.7349   $174.73   $174.75   $174.70  
  Purchase #3 $108.90   9.463%   $119.2052   $119.21   $119.20   $119.20  
  Purchase #4 $218.75   3.200%   $225.75   $225.75   $225.75   $225.80  
  Purchase #5 $71.82   13.870%   $81.7814   $81.78   $81.80   $81.80  
  Purchase #6 $233.80   5.349%   $246.306   $246.31   $246.30   $246.30  
  Purchase #7 $217.45   7.600%   $233.9762   $233.98   $234.00   $234.00  
  7 purchase totals = $1,097.74       $1,167.7632   $1,167.77   $1,167.80   $1,167.80