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 $218.56   7.648%   $235.2755   $235.28   $235.30   $235.30  
  Purchase #2 $132.90   12.755%   $149.8514   $149.85   $149.85   $149.90  
  Purchase #3 $129.96   9.640%   $142.4881   $142.49   $142.50   $142.50  
  Purchase #4 $33.88   7.314%   $36.358   $36.36   $36.35   $36.40  
  Purchase #5 $33.71   7.473%   $36.2291   $36.23   $36.25   $36.20  
  Purchase #6 $250.27   13.332%   $283.636   $283.64   $283.65   $283.60  
  Purchase #7 $207.95   10.524%   $229.8347   $229.83   $229.85   $229.80  
  7 purchase totals = $1,007.23       $1,113.6728   $1,113.68   $1,113.75   $1,113.70