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 $63.37   9.151%   $69.169   $69.17   $69.15   $69.20  
  Purchase #2 $241.39   11.201%   $268.4281   $268.43   $268.45   $268.40  
  Purchase #3 $221.47   11.517%   $246.9767   $246.98   $247.00   $247.00  
  Purchase #4 $232.43   13.194%   $263.0968   $263.10   $263.10   $263.10  
  Purchase #5 $104.51   9.623%   $114.567   $114.57   $114.55   $114.60  
  Purchase #6 $140.34   8.851%   $152.7615   $152.76   $152.75   $152.80  
  Purchase #7 $95.49   4.219%   $99.5187   $99.52   $99.50   $99.50  
  7 purchase totals = $1,099.00       $1,214.5178   $1,214.53   $1,214.50   $1,214.60