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 $162.83   7.214%   $174.5766   $174.58   $174.60   $174.60  
  Purchase #2 $151.89   5.715%   $160.5705   $160.57   $160.55   $160.60  
  Purchase #3 $225.46   4.729%   $236.122   $236.12   $236.10   $236.10  
  Purchase #4 $206.35   7.568%   $221.9666   $221.97   $221.95   $222.00  
  Purchase #5 $182.70   11.174%   $203.1149   $203.11   $203.10   $203.10  
  Purchase #6 $241.47   10.741%   $267.4063   $267.41   $267.40   $267.40  
  Purchase #7 $107.38   13.658%   $122.046   $122.05   $122.05   $122.00  
  7 purchase totals = $1,278.08       $1,385.8029   $1,385.81   $1,385.75   $1,385.80