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 $57.34   8.175%   $62.0275   $62.03   $62.05   $62.00  
  Purchase #2 $206.94   8.627%   $224.7927   $224.79   $224.80   $224.80  
  Purchase #3 $132.51   11.870%   $148.2389   $148.24   $148.25   $148.20  
  Purchase #4 $155.35   11.613%   $173.3908   $173.39   $173.40   $173.40  
  Purchase #5 $142.75   12.146%   $160.0884   $160.09   $160.10   $160.10  
  Purchase #6 $243.83   10.666%   $269.8369   $269.84   $269.85   $269.80  
  Purchase #7 $74.49   7.703%   $80.228   $80.23   $80.25   $80.20  
  7 purchase totals = $1,013.21       $1,118.6032   $1,118.61   $1,118.70   $1,118.50