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 $48.51   4.851%   $50.8632   $50.86   $50.85   $50.90  
  Purchase #2 $169.99   5.566%   $179.4516   $179.45   $179.45   $179.50  
  Purchase #3 $216.55   13.427%   $245.6262   $245.63   $245.65   $245.60  
  Purchase #4 $225.98   4.215%   $235.5051   $235.51   $235.50   $235.50  
  Purchase #5 $60.37   6.165%   $64.0918   $64.09   $64.10   $64.10  
  Purchase #6 $214.34   7.763%   $230.9792   $230.98   $231.00   $231.00  
  Purchase #7 $48.70   6.743%   $51.9838   $51.98   $52.00   $52.00  
  7 purchase totals = $984.44       $1,058.5009   $1,058.50   $1,058.55   $1,058.60