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 $56.92   7.134%   $60.9807   $60.98   $61.00   $61.00  
  Purchase #2 $157.39   7.396%   $169.0306   $169.03   $169.05   $169.00  
  Purchase #3 $94.87   8.263%   $102.7091   $102.71   $102.70   $102.70  
  Purchase #4 $34.57   5.620%   $36.5128   $36.51   $36.50   $36.50  
  Purchase #5 $25.68   7.334%   $27.5634   $27.56   $27.55   $27.60  
  Purchase #6 $88.25   8.536%   $95.783   $95.78   $95.80   $95.80  
  Purchase #7 $220.99   5.234%   $232.5566   $232.56   $232.55   $232.60  
  7 purchase totals = $678.67       $725.1362   $725.13   $725.15   $725.20