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 $72.95   6.506%   $77.6961   $77.70   $77.70   $77.70  
  Purchase #2 $236.28   11.327%   $263.0434   $263.04   $263.05   $263.00  
  Purchase #3 $90.93   4.748%   $95.2474   $95.25   $95.25   $95.20  
  Purchase #4 $159.28   6.337%   $169.3736   $169.37   $169.35   $169.40  
  Purchase #5 $241.49   12.870%   $272.5698   $272.57   $272.55   $272.60  
  Purchase #6 $203.66   11.595%   $227.2744   $227.27   $227.25   $227.30  
  Purchase #7 $83.49   7.162%   $89.4696   $89.47   $89.45   $89.50  
  7 purchase totals = $1,088.08       $1,194.6743   $1,194.67   $1,194.60   $1,194.70