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 $106.46   10.526%   $117.666   $117.67   $117.65   $117.70  
  Purchase #2 $211.52   11.311%   $235.445   $235.45   $235.45   $235.40  
  Purchase #3 $78.76   11.511%   $87.8261   $87.83   $87.85   $87.80  
  Purchase #4 $227.95   5.599%   $240.7129   $240.71   $240.70   $240.70  
  Purchase #5 $35.89   4.206%   $37.3995   $37.40   $37.40   $37.40  
  Purchase #6 $88.77   10.344%   $97.9524   $97.95   $97.95   $98.00  
  Purchase #7 $207.29   4.529%   $216.6782   $216.68   $216.70   $216.70  
  7 purchase totals = $956.64       $1,033.6801   $1,033.69   $1,033.70   $1,033.70