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 $85.68   9.738%   $94.0235   $94.02   $94.00   $94.00  
  Purchase #2 $124.65   13.261%   $141.1798   $141.18   $141.20   $141.20  
  Purchase #3 $211.67   13.515%   $240.2772   $240.28   $240.30   $240.30  
  Purchase #4 $113.87   3.403%   $117.745   $117.75   $117.75   $117.70  
  Purchase #5 $68.43   6.114%   $72.6138   $72.61   $72.60   $72.60  
  Purchase #6 $29.85   7.178%   $31.9926   $31.99   $32.00   $32.00  
  Purchase #7 $58.41   13.799%   $66.47   $66.47   $66.45   $66.50  
  7 purchase totals = $692.56       $764.3019   $764.30   $764.30   $764.30