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 $63.88   11.331%   $71.1182   $71.12   $71.10   $71.10  
  Purchase #2 $195.51   11.250%   $217.5049   $217.50   $217.50   $217.50  
  Purchase #3 $153.66   8.378%   $166.5336   $166.53   $166.55   $166.50  
  Purchase #4 $56.35   9.590%   $61.754   $61.75   $61.75   $61.80  
  Purchase #5 $127.42   4.447%   $133.0864   $133.09   $133.10   $133.10  
  Purchase #6 $193.27   12.801%   $218.0105   $218.01   $218.00   $218.00  
  Purchase #7 $201.80   13.616%   $229.2771   $229.28   $229.30   $229.30  
  7 purchase totals = $991.89       $1,097.2847   $1,097.28   $1,097.30   $1,097.30