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 $194.71   6.846%   $208.0398   $208.04   $208.05   $208.00  
  Purchase #2 $193.97   10.226%   $213.8054   $213.81   $213.80   $213.80  
  Purchase #3 $160.43   6.529%   $170.9045   $170.90   $170.90   $170.90  
  Purchase #4 $220.67   3.455%   $228.2941   $228.29   $228.30   $228.30  
  Purchase #5 $88.62   6.240%   $94.1499   $94.15   $94.15   $94.10  
  Purchase #6 $193.85   8.217%   $209.7787   $209.78   $209.80   $209.80  
  Purchase #7 $201.52   7.232%   $216.0939   $216.09   $216.10   $216.10  
  7 purchase totals = $1,253.77       $1,341.0663   $1,341.06   $1,341.10   $1,341.00