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 $215.40   13.623%   $244.7439   $244.74   $244.75   $244.70  
  Purchase #2 $203.25   7.584%   $218.6645   $218.66   $218.65   $218.70  
  Purchase #3 $46.70   7.578%   $50.2389   $50.24   $50.25   $50.20  
  Purchase #4 $128.55   12.232%   $144.2742   $144.27   $144.25   $144.30  
  Purchase #5 $88.44   10.544%   $97.7651   $97.77   $97.75   $97.80  
  Purchase #6 $152.43   11.691%   $170.2506   $170.25   $170.25   $170.30  
  Purchase #7 $169.26   6.375%   $180.0503   $180.05   $180.05   $180.10  
  7 purchase totals = $1,004.03       $1,105.9875   $1,105.98   $1,105.95   $1,106.10