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 $240.78   5.477%   $253.9675   $253.97   $253.95   $254.00  
  Purchase #2 $13.56   5.698%   $14.3326   $14.33   $14.35   $14.30  
  Purchase #3 $175.71   9.298%   $192.0475   $192.05   $192.05   $192.00  
  Purchase #4 $24.71   7.753%   $26.6258   $26.63   $26.65   $26.60  
  Purchase #5 $199.82   10.290%   $220.3815   $220.38   $220.40   $220.40  
  Purchase #6 $214.92   3.411%   $222.2509   $222.25   $222.25   $222.30  
  Purchase #7 $157.27   6.582%   $167.6215   $167.62   $167.60   $167.60  
  7 purchase totals = $1,026.77       $1,097.2273   $1,097.23   $1,097.25   $1,097.20