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 $213.98   4.417%   $223.4315   $223.43   $223.45   $223.40  
  Purchase #2 $228.28   5.325%   $240.4359   $240.44   $240.45   $240.40  
  Purchase #3 $150.39   12.451%   $169.1151   $169.12   $169.10   $169.10  
  Purchase #4 $191.72   11.547%   $213.8579   $213.86   $213.85   $213.90  
  Purchase #5 $66.55   7.692%   $71.669   $71.67   $71.65   $71.70  
  Purchase #6 $26.42   3.126%   $27.2459   $27.25   $27.25   $27.20  
  Purchase #7 $236.32   13.779%   $268.8825   $268.88   $268.90   $268.90  
  7 purchase totals = $1,113.66       $1,214.6378   $1,214.65   $1,214.65   $1,214.60