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 $54.76   10.674%   $60.6051   $60.61   $60.60   $60.60  
  Purchase #2 $221.39   6.127%   $234.9546   $234.95   $234.95   $235.00  
  Purchase #3 $36.99   3.360%   $38.2329   $38.23   $38.25   $38.20  
  Purchase #4 $152.82   5.554%   $161.3076   $161.31   $161.30   $161.30  
  Purchase #5 $116.56   10.220%   $128.4724   $128.47   $128.45   $128.50  
  Purchase #6 $93.77   6.232%   $99.6137   $99.61   $99.60   $99.60  
  Purchase #7 $56.60   3.411%   $58.5306   $58.53   $58.55   $58.50  
  7 purchase totals = $732.89       $781.7169   $781.71   $781.70   $781.70