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 $183.71   5.557%   $193.9188   $193.92   $193.90   $193.90  
  Purchase #2 $230.41   4.738%   $241.3268   $241.33   $241.35   $241.30  
  Purchase #3 $148.74   5.512%   $156.9385   $156.94   $156.95   $156.90  
  Purchase #4 $141.75   13.122%   $160.3504   $160.35   $160.35   $160.40  
  Purchase #5 $238.85   10.480%   $263.8815   $263.88   $263.90   $263.90  
  Purchase #6 $236.60   12.834%   $266.9652   $266.97   $266.95   $267.00  
  Purchase #7 $231.50   7.529%   $248.9296   $248.93   $248.95   $248.90  
  7 purchase totals = $1,411.56       $1,532.3108   $1,532.32   $1,532.35   $1,532.30