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 $23.72   9.523%   $25.9789   $25.98   $26.00   $26.00  
  Purchase #2 $187.49   9.537%   $205.3709   $205.37   $205.35   $205.40  
  Purchase #3 $202.55   4.276%   $211.211   $211.21   $211.20   $211.20  
  Purchase #4 $15.84   13.604%   $17.9949   $17.99   $18.00   $18.00  
  Purchase #5 $94.87   5.512%   $100.0992   $100.10   $100.10   $100.10  
  Purchase #6 $221.96   3.272%   $229.2225   $229.22   $229.20   $229.20  
  Purchase #7 $141.83   10.478%   $156.6909   $156.69   $156.70   $156.70  
  7 purchase totals = $888.26       $946.5683   $946.56   $946.55   $946.60