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 $66.91   11.518%   $74.6167   $74.62   $74.60   $74.60  
  Purchase #2 $238.68   6.153%   $253.366   $253.37   $253.35   $253.40  
  Purchase #3 $30.36   8.501%   $32.9409   $32.94   $32.95   $32.90  
  Purchase #4 $87.90   8.729%   $95.5728   $95.57   $95.55   $95.60  
  Purchase #5 $160.32   7.779%   $172.7913   $172.79   $172.80   $172.80  
  Purchase #6 $27.50   7.613%   $29.5936   $29.59   $29.60   $29.60  
  Purchase #7 $200.49   11.540%   $223.6265   $223.63   $223.65   $223.60  
  7 purchase totals = $812.16       $882.5078   $882.51   $882.50   $882.50