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 $71.48   7.165%   $76.6015   $76.60   $76.60   $76.60  
  Purchase #2 $116.50   10.174%   $128.3527   $128.35   $128.35   $128.40  
  Purchase #3 $66.41   7.571%   $71.4379   $71.44   $71.45   $71.40  
  Purchase #4 $126.73   6.607%   $135.1031   $135.10   $135.10   $135.10  
  Purchase #5 $187.41   5.586%   $197.8787   $197.88   $197.90   $197.90  
  Purchase #6 $220.55   8.703%   $239.7445   $239.74   $239.75   $239.70  
  Purchase #7 $164.65   7.230%   $176.5542   $176.55   $176.55   $176.60  
  7 purchase totals = $953.73       $1,025.6726   $1,025.66   $1,025.70   $1,025.70