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 $58.85   6.712%   $62.8   $62.80   $62.80   $62.80  
  Purchase #2 $124.82   3.561%   $129.2648   $129.26   $129.25   $129.30  
  Purchase #3 $190.99   3.271%   $197.2373   $197.24   $197.25   $197.20  
  Purchase #4 $234.41   10.839%   $259.8177   $259.82   $259.80   $259.80  
  Purchase #5 $146.30   4.764%   $153.2697   $153.27   $153.25   $153.30  
  Purchase #6 $139.94   9.359%   $153.037   $153.04   $153.05   $153.00  
  Purchase #7 $55.41   5.232%   $58.3091   $58.31   $58.30   $58.30  
  7 purchase totals = $950.72       $1,013.7356   $1,013.74   $1,013.70   $1,013.70