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 $237.75   6.865%   $254.0715   $254.07   $254.05   $254.10  
  Purchase #2 $56.39   8.521%   $61.195   $61.20   $61.20   $61.20  
  Purchase #3 $154.28   7.290%   $165.527   $165.53   $165.55   $165.50  
  Purchase #4 $72.61   7.388%   $77.9744   $77.97   $77.95   $78.00  
  Purchase #5 $142.32   4.495%   $148.7173   $148.72   $148.70   $148.70  
  Purchase #6 $196.61   11.395%   $219.0137   $219.01   $219.00   $219.00  
  Purchase #7 $116.63   7.202%   $125.0297   $125.03   $125.05   $125.00  
  7 purchase totals = $976.59       $1,051.5286   $1,051.53   $1,051.50   $1,051.50