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 $54.80   13.667%   $62.2895   $62.29   $62.30   $62.30  
  Purchase #2 $245.94   10.699%   $272.2531   $272.25   $272.25   $272.30  
  Purchase #3 $167.95   8.720%   $182.5952   $182.60   $182.60   $182.60  
  Purchase #4 $195.45   8.292%   $211.6567   $211.66   $211.65   $211.70  
  Purchase #5 $197.62   4.691%   $206.8904   $206.89   $206.90   $206.90  
  Purchase #6 $101.93   10.529%   $112.6622   $112.66   $112.65   $112.70  
  Purchase #7 $92.53   3.142%   $95.4373   $95.44   $95.45   $95.40  
  7 purchase totals = $1,056.22       $1,143.7844   $1,143.79   $1,143.80   $1,143.90