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 $62.30   10.112%   $68.5998   $68.60   $68.60   $68.60  
  Purchase #2 $214.61   9.559%   $235.1246   $235.12   $235.10   $235.10  
  Purchase #3 $221.95   4.390%   $231.6936   $231.69   $231.70   $231.70  
  Purchase #4 $169.33   3.315%   $174.9433   $174.94   $174.95   $174.90  
  Purchase #5 $85.45   8.576%   $92.7782   $92.78   $92.80   $92.80  
  Purchase #6 $51.99   4.667%   $54.4164   $54.42   $54.40   $54.40  
  Purchase #7 $52.27   11.403%   $58.2303   $58.23   $58.25   $58.20  
  7 purchase totals = $857.90       $915.7862   $915.78   $915.80   $915.70