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 $96.43   13.762%   $109.7007   $109.70   $109.70   $109.70  
  Purchase #2 $170.67   9.336%   $186.6038   $186.60   $186.60   $186.60  
  Purchase #3 $82.26   11.718%   $91.8992   $91.90   $91.90   $91.90  
  Purchase #4 $90.27   5.210%   $94.9731   $94.97   $94.95   $95.00  
  Purchase #5 $181.45   6.855%   $193.8884   $193.89   $193.90   $193.90  
  Purchase #6 $194.39   6.426%   $206.8815   $206.88   $206.90   $206.90  
  Purchase #7 $236.37   10.283%   $260.6759   $260.68   $260.70   $260.70  
  7 purchase totals = $1,051.84       $1,144.6226   $1,144.62   $1,144.65   $1,144.70