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 $237.32   12.722%   $267.5119   $267.51   $267.50   $267.50  
  Purchase #2 $18.33   4.707%   $19.1928   $19.19   $19.20   $19.20  
  Purchase #3 $61.99   11.635%   $69.2025   $69.20   $69.20   $69.20  
  Purchase #4 $165.43   3.552%   $171.3061   $171.31   $171.30   $171.30  
  Purchase #5 $248.54   7.669%   $267.6005   $267.60   $267.60   $267.60  
  Purchase #6 $233.88   12.597%   $263.3419   $263.34   $263.35   $263.30  
  Purchase #7 $99.72   5.262%   $104.9673   $104.97   $104.95   $105.00  
  7 purchase totals = $1,065.21       $1,163.1230   $1,163.12   $1,163.10   $1,163.10