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 $213.97   9.254%   $233.7708   $233.77   $233.75   $233.80  
  Purchase #2 $74.89   10.311%   $82.6119   $82.61   $82.60   $82.60  
  Purchase #3 $12.92   5.263%   $13.6   $13.60   $13.60   $13.60  
  Purchase #4 $205.56   10.132%   $226.3873   $226.39   $226.40   $226.40  
  Purchase #5 $237.48   8.224%   $257.0104   $257.01   $257.00   $257.00  
  Purchase #6 $61.30   11.291%   $68.2214   $68.22   $68.20   $68.20  
  Purchase #7 $159.44   13.357%   $180.7364   $180.74   $180.75   $180.70  
  7 purchase totals = $965.56       $1,062.3382   $1,062.34   $1,062.30   $1,062.30