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 $208.75   11.751%   $233.2802   $233.28   $233.30   $233.30  
  Purchase #2 $39.47   11.349%   $43.9495   $43.95   $43.95   $43.90  
  Purchase #3 $81.92   7.587%   $88.1353   $88.14   $88.15   $88.10  
  Purchase #4 $94.90   8.786%   $103.2379   $103.24   $103.25   $103.20  
  Purchase #5 $165.41   7.218%   $177.3493   $177.35   $177.35   $177.30  
  Purchase #6 $99.49   13.285%   $112.7072   $112.71   $112.70   $112.70  
  Purchase #7 $43.96   7.709%   $47.3489   $47.35   $47.35   $47.30  
  7 purchase totals = $733.90       $806.0083   $806.02   $806.05   $805.80