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 $71.47   6.509%   $76.122   $76.12   $76.10   $76.10  
  Purchase #2 $109.89   6.329%   $116.8449   $116.84   $116.85   $116.80  
  Purchase #3 $169.94   3.329%   $175.5973   $175.60   $175.60   $175.60  
  Purchase #4 $86.46   8.154%   $93.5099   $93.51   $93.50   $93.50  
  Purchase #5 $183.28   5.647%   $193.6298   $193.63   $193.65   $193.60  
  Purchase #6 $168.56   11.289%   $187.5887   $187.59   $187.60   $187.60  
  Purchase #7 $13.46   5.511%   $14.2018   $14.20   $14.20   $14.20  
  7 purchase totals = $803.06       $857.4944   $857.49   $857.50   $857.40