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 $180.27   11.676%   $201.3183   $201.32   $201.30   $201.30  
  Purchase #2 $93.26   4.546%   $97.4996   $97.50   $97.50   $97.50  
  Purchase #3 $147.46   9.831%   $161.9568   $161.96   $161.95   $162.00  
  Purchase #4 $177.61   10.511%   $196.2786   $196.28   $196.30   $196.30  
  Purchase #5 $105.30   5.651%   $111.2505   $111.25   $111.25   $111.30  
  Purchase #6 $140.77   13.245%   $159.415   $159.42   $159.40   $159.40  
  Purchase #7 $129.35   4.560%   $135.2484   $135.25   $135.25   $135.20  
  7 purchase totals = $974.02       $1,062.9672   $1,062.98   $1,062.95   $1,063.00