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 $208.65   13.468%   $236.751   $236.75   $236.75   $236.80  
  Purchase #2 $153.68   4.240%   $160.196   $160.20   $160.20   $160.20  
  Purchase #3 $165.25   5.481%   $174.3074   $174.31   $174.30   $174.30  
  Purchase #4 $76.48   4.320%   $79.7839   $79.78   $79.80   $79.80  
  Purchase #5 $157.29   11.825%   $175.8895   $175.89   $175.90   $175.90  
  Purchase #6 $43.94   9.270%   $48.0132   $48.01   $48.00   $48.00  
  Purchase #7 $6.98   8.474%   $7.5715   $7.57   $7.55   $7.60  
  7 purchase totals = $812.27       $882.5125   $882.51   $882.50   $882.60