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 $214.49   5.658%   $226.6258   $226.63   $226.65   $226.60  
  Purchase #2 $43.98   3.788%   $45.646   $45.65   $45.65   $45.60  
  Purchase #3 $138.68   13.809%   $157.8303   $157.83   $157.85   $157.80  
  Purchase #4 $239.44   12.656%   $269.7435   $269.74   $269.75   $269.70  
  Purchase #5 $162.76   11.714%   $181.8257   $181.83   $181.85   $181.80  
  Purchase #6 $94.33   11.201%   $104.8959   $104.90   $104.90   $104.90  
  Purchase #7 $68.64   12.171%   $76.9942   $76.99   $77.00   $77.00  
  7 purchase totals = $962.32       $1,063.5614   $1,063.57   $1,063.65   $1,063.40