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 $208.52   10.874%   $231.1945   $231.19   $231.20   $231.20  
  Purchase #2 $229.93   5.138%   $241.7438   $241.74   $241.75   $241.70  
  Purchase #3 $184.25   3.257%   $190.251   $190.25   $190.25   $190.30  
  Purchase #4 $52.77   10.827%   $58.4834   $58.48   $58.50   $58.50  
  Purchase #5 $92.80   12.871%   $104.7443   $104.74   $104.75   $104.70  
  Purchase #6 $191.64   3.863%   $199.0431   $199.04   $199.05   $199.00  
  Purchase #7 $148.38   12.286%   $166.61   $166.61   $166.60   $166.60  
  7 purchase totals = $1,108.29       $1,192.0701   $1,192.05   $1,192.10   $1,192.00