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 $41.52   4.160%   $43.2472   $43.25   $43.25   $43.20  
  Purchase #2 $9.92   6.307%   $10.5457   $10.55   $10.55   $10.50  
  Purchase #3 $234.32   4.500%   $244.8644   $244.86   $244.85   $244.90  
  Purchase #4 $195.81   3.370%   $202.4088   $202.41   $202.40   $202.40  
  Purchase #5 $179.37   3.351%   $185.3807   $185.38   $185.40   $185.40  
  Purchase #6 $235.68   11.279%   $262.2623   $262.26   $262.25   $262.30  
  Purchase #7 $42.93   9.352%   $46.9448   $46.94   $46.95   $46.90  
  7 purchase totals = $939.55       $995.6539   $995.65   $995.65   $995.60