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 $106.93   8.809%   $116.3495   $116.35   $116.35   $116.30  
  Purchase #2 $93.78   8.461%   $101.7147   $101.71   $101.70   $101.70  
  Purchase #3 $98.36   5.307%   $103.58   $103.58   $103.60   $103.60  
  Purchase #4 $105.56   6.314%   $112.2251   $112.23   $112.25   $112.20  
  Purchase #5 $244.47   8.475%   $265.1888   $265.19   $265.20   $265.20  
  Purchase #6 $224.95   13.778%   $255.9436   $255.94   $255.95   $255.90  
  Purchase #7 $200.52   10.194%   $220.961   $220.96   $220.95   $221.00  
  7 purchase totals = $1,074.57       $1,175.9627   $1,175.96   $1,176.00   $1,175.90