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 $86.33   10.460%   $95.3601   $95.36   $95.35   $95.40  
  Purchase #2 $167.50   10.795%   $185.5816   $185.58   $185.60   $185.60  
  Purchase #3 $181.68   6.779%   $193.9961   $194.00   $194.00   $194.00  
  Purchase #4 $66.75   12.832%   $75.3154   $75.32   $75.30   $75.30  
  Purchase #5 $92.40   8.694%   $100.4333   $100.43   $100.45   $100.40  
  Purchase #6 $32.36   8.602%   $35.1436   $35.14   $35.15   $35.10  
  Purchase #7 $62.27   10.256%   $68.6564   $68.66   $68.65   $68.70  
  7 purchase totals = $689.29       $754.4865   $754.49   $754.50   $754.50