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 $62.57   11.268%   $69.6204   $69.62   $69.60   $69.60  
  Purchase #2 $206.83   11.191%   $229.9763   $229.98   $230.00   $230.00  
  Purchase #3 $124.39   8.693%   $135.2032   $135.20   $135.20   $135.20  
  Purchase #4 $172.35   13.874%   $196.2618   $196.26   $196.25   $196.30  
  Purchase #5 $195.58   9.479%   $214.119   $214.12   $214.10   $214.10  
  Purchase #6 $226.51   9.177%   $247.2968   $247.30   $247.30   $247.30  
  Purchase #7 $104.52   10.168%   $115.1476   $115.15   $115.15   $115.10  
  7 purchase totals = $1,092.75       $1,207.6251   $1,207.63   $1,207.60   $1,207.60