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 $95.41   3.711%   $98.9507   $98.95   $98.95   $99.00  
  Purchase #2 $200.80   11.114%   $223.1169   $223.12   $223.10   $223.10  
  Purchase #3 $148.59   3.814%   $154.2572   $154.26   $154.25   $154.30  
  Purchase #4 $68.41   12.355%   $76.8621   $76.86   $76.85   $76.90  
  Purchase #5 $148.57   11.720%   $165.9824   $165.98   $166.00   $166.00  
  Purchase #6 $89.35   4.196%   $93.0991   $93.10   $93.10   $93.10  
  Purchase #7 $182.44   13.339%   $206.7757   $206.78   $206.80   $206.80  
  7 purchase totals = $933.57       $1,019.0441   $1,019.05   $1,019.05   $1,019.20