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 $54.84   13.511%   $62.2494   $62.25   $62.25   $62.20  
  Purchase #2 $55.55   8.346%   $60.1862   $60.19   $60.20   $60.20  
  Purchase #3 $216.62   4.792%   $227.0004   $227.00   $227.00   $227.00  
  Purchase #4 $217.65   11.665%   $243.0389   $243.04   $243.05   $243.00  
  Purchase #5 $207.51   5.823%   $219.5933   $219.59   $219.60   $219.60  
  Purchase #6 $249.28   6.671%   $265.9095   $265.91   $265.90   $265.90  
  Purchase #7 $51.50   7.332%   $55.276   $55.28   $55.30   $55.30  
  7 purchase totals = $1,052.95       $1,133.2537   $1,133.26   $1,133.30   $1,133.20