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 $182.64   6.300%   $194.1463   $194.15   $194.15   $194.10  
  Purchase #2 $79.86   3.567%   $82.7086   $82.71   $82.70   $82.70  
  Purchase #3 $173.27   7.571%   $186.3883   $186.39   $186.40   $186.40  
  Purchase #4 $31.57   6.192%   $33.5248   $33.52   $33.50   $33.50  
  Purchase #5 $191.43   9.438%   $209.4972   $209.50   $209.50   $209.50  
  Purchase #6 $148.58   4.173%   $154.7802   $154.78   $154.80   $154.80  
  Purchase #7 $177.90   8.619%   $193.2332   $193.23   $193.25   $193.20  
  7 purchase totals = $985.25       $1,054.2786   $1,054.28   $1,054.30   $1,054.20