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 $93.27   4.743%   $97.6938   $97.69   $97.70   $97.70  
  Purchase #2 $233.79   11.329%   $260.2761   $260.28   $260.30   $260.30  
  Purchase #3 $26.52   3.725%   $27.5079   $27.51   $27.50   $27.50  
  Purchase #4 $145.39   11.306%   $161.8278   $161.83   $161.85   $161.80  
  Purchase #5 $246.34   6.605%   $262.6108   $262.61   $262.60   $262.60  
  Purchase #6 $180.83   11.760%   $202.0956   $202.10   $202.10   $202.10  
  Purchase #7 $51.39   3.374%   $53.1239   $53.12   $53.10   $53.10  
  7 purchase totals = $977.53       $1,065.1359   $1,065.14   $1,065.15   $1,065.10