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 $207.93   9.495%   $227.673   $227.67   $227.65   $227.70  
  Purchase #2 $57.63   8.533%   $62.5476   $62.55   $62.55   $62.50  
  Purchase #3 $199.81   10.840%   $221.4694   $221.47   $221.45   $221.50  
  Purchase #4 $207.50   5.292%   $218.4809   $218.48   $218.50   $218.50  
  Purchase #5 $92.86   4.232%   $96.7898   $96.79   $96.80   $96.80  
  Purchase #6 $161.46   3.578%   $167.237   $167.24   $167.25   $167.20  
  Purchase #7 $48.37   3.199%   $49.9174   $49.92   $49.90   $49.90  
  7 purchase totals = $975.56       $1,044.1151   $1,044.12   $1,044.10   $1,044.10