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 $194.52   11.532%   $216.952   $216.95   $216.95   $217.00  
  Purchase #2 $55.98   3.735%   $58.0709   $58.07   $58.05   $58.10  
  Purchase #3 $157.89   6.444%   $168.0644   $168.06   $168.05   $168.10  
  Purchase #4 $153.71   11.189%   $170.9086   $170.91   $170.90   $170.90  
  Purchase #5 $91.73   9.843%   $100.759   $100.76   $100.75   $100.80  
  Purchase #6 $171.84   12.103%   $192.6378   $192.64   $192.65   $192.60  
  Purchase #7 $213.66   10.676%   $236.4703   $236.47   $236.45   $236.50  
  7 purchase totals = $1,039.33       $1,143.8630   $1,143.86   $1,143.80   $1,144.00