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 $87.26   5.570%   $92.1204   $92.12   $92.10   $92.10  
  Purchase #2 $231.83   3.340%   $239.5731   $239.57   $239.55   $239.60  
  Purchase #3 $51.62   12.551%   $58.0988   $58.10   $58.10   $58.10  
  Purchase #4 $51.68   13.477%   $58.6449   $58.64   $58.65   $58.60  
  Purchase #5 $197.55   4.455%   $206.3509   $206.35   $206.35   $206.40  
  Purchase #6 $241.78   8.364%   $262.0025   $262.00   $262.00   $262.00  
  Purchase #7 $220.26   8.433%   $238.8345   $238.83   $238.85   $238.80  
  7 purchase totals = $1,081.98       $1,155.6251   $1,155.61   $1,155.60   $1,155.60