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 $82.83   3.547%   $85.768   $85.77   $85.75   $85.80  
  Purchase #2 $192.59   5.751%   $203.6659   $203.67   $203.65   $203.70  
  Purchase #3 $54.91   5.151%   $57.7384   $57.74   $57.75   $57.70  
  Purchase #4 $23.84   11.572%   $26.5988   $26.60   $26.60   $26.60  
  Purchase #5 $75.31   4.443%   $78.656   $78.66   $78.65   $78.70  
  Purchase #6 $140.88   8.337%   $152.6252   $152.63   $152.65   $152.60  
  Purchase #7 $128.51   10.756%   $142.3325   $142.33   $142.35   $142.30  
  7 purchase totals = $698.87       $747.3848   $747.40   $747.40   $747.40