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 $173.31   12.535%   $195.0344   $195.03   $195.05   $195.00  
  Purchase #2 $50.60   10.597%   $55.9621   $55.96   $55.95   $56.00  
  Purchase #3 $89.25   6.280%   $94.8549   $94.85   $94.85   $94.90  
  Purchase #4 $153.77   7.718%   $165.638   $165.64   $165.65   $165.60  
  Purchase #5 $179.54   10.568%   $198.5138   $198.51   $198.50   $198.50  
  Purchase #6 $41.28   8.658%   $44.854   $44.85   $44.85   $44.90  
  Purchase #7 $11.61   11.114%   $12.9003   $12.90   $12.90   $12.90  
  7 purchase totals = $699.36       $767.7575   $767.74   $767.75   $767.80