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 $86.62   11.739%   $96.7883   $96.79   $96.80   $96.80  
  Purchase #2 $92.25   6.424%   $98.1761   $98.18   $98.20   $98.20  
  Purchase #3 $119.44   6.198%   $126.8429   $126.84   $126.85   $126.80  
  Purchase #4 $106.59   5.410%   $112.3565   $112.36   $112.35   $112.40  
  Purchase #5 $193.97   11.533%   $216.3406   $216.34   $216.35   $216.30  
  Purchase #6 $220.50   5.286%   $232.1556   $232.16   $232.15   $232.20  
  Purchase #7 $59.88   6.107%   $63.5369   $63.54   $63.55   $63.50  
  7 purchase totals = $879.25       $946.1969   $946.21   $946.25   $946.20