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 $86.59   10.862%   $95.9954   $96.00   $96.00   $96.00  
  Purchase #2 $6.88   4.174%   $7.1672   $7.17   $7.15   $7.20  
  Purchase #3 $201.63   13.645%   $229.1424   $229.14   $229.15   $229.10  
  Purchase #4 $216.78   7.823%   $233.7387   $233.74   $233.75   $233.70  
  Purchase #5 $119.52   10.322%   $131.8569   $131.86   $131.85   $131.90  
  Purchase #6 $242.40   11.797%   $270.9959   $271.00   $271.00   $271.00  
  Purchase #7 $184.59   8.482%   $200.2469   $200.25   $200.25   $200.20  
  7 purchase totals = $1,058.39       $1,169.1434   $1,169.16   $1,169.15   $1,169.10