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 $106.39   7.114%   $113.9586   $113.96   $113.95   $114.00  
  Purchase #2 $217.38   5.689%   $229.7467   $229.75   $229.75   $229.70  
  Purchase #3 $166.71   11.182%   $185.3515   $185.35   $185.35   $185.40  
  Purchase #4 $176.91   10.413%   $195.3316   $195.33   $195.35   $195.30  
  Purchase #5 $148.46   8.846%   $161.5928   $161.59   $161.60   $161.60  
  Purchase #6 $90.93   6.565%   $96.8996   $96.90   $96.90   $96.90  
  Purchase #7 $26.31   5.748%   $27.8223   $27.82   $27.80   $27.80  
  7 purchase totals = $933.09       $1,010.7031   $1,010.70   $1,010.70   $1,010.70