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 $183.58   7.614%   $197.5578   $197.56   $197.55   $197.60  
  Purchase #2 $165.86   10.478%   $183.2388   $183.24   $183.25   $183.20  
  Purchase #3 $51.69   6.404%   $55.0002   $55.00   $55.00   $55.00  
  Purchase #4 $12.94   7.373%   $13.8941   $13.89   $13.90   $13.90  
  Purchase #5 $77.70   7.332%   $83.397   $83.40   $83.40   $83.40  
  Purchase #6 $119.59   4.237%   $124.657   $124.66   $124.65   $124.70  
  Purchase #7 $87.75   11.660%   $97.9817   $97.98   $98.00   $98.00  
  7 purchase totals = $699.11       $755.7266   $755.73   $755.75   $755.80