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 $244.53   9.466%   $267.6772   $267.68   $267.70   $267.70  
  Purchase #2 $106.94   9.421%   $117.0148   $117.01   $117.00   $117.00  
  Purchase #3 $113.29   13.801%   $128.9252   $128.93   $128.95   $128.90  
  Purchase #4 $71.30   3.205%   $73.5852   $73.59   $73.60   $73.60  
  Purchase #5 $73.62   5.840%   $77.9194   $77.92   $77.90   $77.90  
  Purchase #6 $185.75   13.806%   $211.3946   $211.39   $211.40   $211.40  
  Purchase #7 $163.51   5.816%   $173.0197   $173.02   $173.00   $173.00  
  7 purchase totals = $958.94       $1,049.5361   $1,049.54   $1,049.55   $1,049.50