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 $59.84   8.669%   $65.0275   $65.03   $65.05   $65.00  
  Purchase #2 $213.90   9.424%   $234.0579   $234.06   $234.05   $234.10  
  Purchase #3 $99.65   3.730%   $103.3669   $103.37   $103.35   $103.40  
  Purchase #4 $184.98   7.644%   $199.1199   $199.12   $199.10   $199.10  
  Purchase #5 $89.51   6.504%   $95.3317   $95.33   $95.35   $95.30  
  Purchase #6 $208.42   6.424%   $221.8089   $221.81   $221.80   $221.80  
  Purchase #7 $184.93   7.662%   $199.0993   $199.10   $199.10   $199.10  
  7 purchase totals = $1,041.23       $1,117.8121   $1,117.82   $1,117.80   $1,117.80