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 $56.32   10.195%   $62.0618   $62.06   $62.05   $62.10  
  Purchase #2 $239.49   13.841%   $272.6378   $272.64   $272.65   $272.60  
  Purchase #3 $174.98   8.396%   $189.6713   $189.67   $189.65   $189.70  
  Purchase #4 $99.25   4.760%   $103.9743   $103.97   $103.95   $104.00  
  Purchase #5 $117.43   12.187%   $131.7412   $131.74   $131.75   $131.70  
  Purchase #6 $249.52   4.256%   $260.1396   $260.14   $260.15   $260.10  
  Purchase #7 $183.99   13.732%   $209.2555   $209.26   $209.25   $209.30  
  7 purchase totals = $1,120.98       $1,229.4815   $1,229.48   $1,229.45   $1,229.50