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 $55.59   11.439%   $61.9489   $61.95   $61.95   $61.90  
  Purchase #2 $247.63   8.228%   $268.005   $268.01   $268.00   $268.00  
  Purchase #3 $118.65   13.565%   $134.7449   $134.74   $134.75   $134.70  
  Purchase #4 $102.49   3.759%   $106.3426   $106.34   $106.35   $106.30  
  Purchase #5 $59.56   13.186%   $67.4136   $67.41   $67.40   $67.40  
  Purchase #6 $171.59   5.790%   $181.5251   $181.53   $181.55   $181.50  
  Purchase #7 $63.43   4.746%   $66.4404   $66.44   $66.45   $66.40  
  7 purchase totals = $818.94       $886.4205   $886.42   $886.45   $886.20