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 $215.47   9.470%   $235.875   $235.88   $235.90   $235.90  
  Purchase #2 $196.45   12.161%   $220.3403   $220.34   $220.35   $220.30  
  Purchase #3 $46.48   5.158%   $48.8774   $48.88   $48.90   $48.90  
  Purchase #4 $64.55   3.614%   $66.8828   $66.88   $66.90   $66.90  
  Purchase #5 $216.30   9.440%   $236.7187   $236.72   $236.70   $236.70  
  Purchase #6 $97.63   8.854%   $106.2742   $106.27   $106.25   $106.30  
  Purchase #7 $156.68   8.258%   $169.6186   $169.62   $169.60   $169.60  
  7 purchase totals = $993.56       $1,084.5870   $1,084.59   $1,084.60   $1,084.60