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 $58.67   6.541%   $62.5076   $62.51   $62.50   $62.50  
  Purchase #2 $221.41   5.603%   $233.8156   $233.82   $233.80   $233.80  
  Purchase #3 $63.46   8.616%   $68.9277   $68.93   $68.95   $68.90  
  Purchase #4 $32.64   10.631%   $36.11   $36.11   $36.10   $36.10  
  Purchase #5 $202.60   11.803%   $226.5129   $226.51   $226.50   $226.50  
  Purchase #6 $176.36   3.485%   $182.5061   $182.51   $182.50   $182.50  
  Purchase #7 $183.31   10.534%   $202.6199   $202.62   $202.60   $202.60  
  7 purchase totals = $938.45       $1,012.9998   $1,013.01   $1,012.95   $1,012.90