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 $119.65   4.700%   $125.2736   $125.27   $125.25   $125.30  
  Purchase #2 $244.92   10.366%   $270.3084   $270.31   $270.30   $270.30  
  Purchase #3 $46.35   12.471%   $52.1303   $52.13   $52.15   $52.10  
  Purchase #4 $46.96   13.337%   $53.2231   $53.22   $53.20   $53.20  
  Purchase #5 $184.98   4.665%   $193.6093   $193.61   $193.60   $193.60  
  Purchase #6 $165.76   7.351%   $177.945   $177.95   $177.95   $177.90  
  Purchase #7 $38.77   11.744%   $43.3231   $43.32   $43.30   $43.30  
  7 purchase totals = $847.39       $915.8128   $915.81   $915.75   $915.70