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 $158.64   9.666%   $173.9741   $173.97   $173.95   $174.00  
  Purchase #2 $93.33   4.591%   $97.6148   $97.61   $97.60   $97.60  
  Purchase #3 $243.95   8.231%   $264.0295   $264.03   $264.05   $264.00  
  Purchase #4 $243.64   5.498%   $257.0353   $257.04   $257.05   $257.00  
  Purchase #5 $179.64   8.314%   $194.5753   $194.58   $194.60   $194.60  
  Purchase #6 $199.89   5.812%   $211.5076   $211.51   $211.50   $211.50  
  Purchase #7 $130.73   12.662%   $147.283   $147.28   $147.30   $147.30  
  7 purchase totals = $1,249.82       $1,346.0196   $1,346.02   $1,346.05   $1,346.00