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 $105.94   12.585%   $119.2725   $119.27   $119.25   $119.30  
  Purchase #2 $55.38   9.602%   $60.6976   $60.70   $60.70   $60.70  
  Purchase #3 $50.91   5.339%   $53.6281   $53.63   $53.65   $53.60  
  Purchase #4 $230.42   6.336%   $245.0194   $245.02   $245.00   $245.00  
  Purchase #5 $144.81   4.558%   $151.4104   $151.41   $151.40   $151.40  
  Purchase #6 $188.57   7.148%   $202.049   $202.05   $202.05   $202.00  
  Purchase #7 $48.91   11.552%   $54.5601   $54.56   $54.55   $54.60  
  7 purchase totals = $824.94       $886.6371   $886.64   $886.60   $886.60