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 $195.50   5.731%   $206.7041   $206.70   $206.70   $206.70  
  Purchase #2 $240.67   10.826%   $266.7249   $266.72   $266.70   $266.70  
  Purchase #3 $56.97   6.415%   $60.6246   $60.62   $60.60   $60.60  
  Purchase #4 $22.65   10.582%   $25.0468   $25.05   $25.05   $25.00  
  Purchase #5 $209.82   11.452%   $233.8486   $233.85   $233.85   $233.80  
  Purchase #6 $159.93   10.704%   $177.0489   $177.05   $177.05   $177.00  
  Purchase #7 $87.63   5.777%   $92.6924   $92.69   $92.70   $92.70  
  7 purchase totals = $973.17       $1,062.6903   $1,062.68   $1,062.65   $1,062.50