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 $167.26   11.499%   $186.4932   $186.49   $186.50   $186.50  
  Purchase #2 $97.33   11.528%   $108.5502   $108.55   $108.55   $108.60  
  Purchase #3 $24.45   5.802%   $25.8686   $25.87   $25.85   $25.90  
  Purchase #4 $115.63   6.188%   $122.7852   $122.79   $122.80   $122.80  
  Purchase #5 $175.40   9.674%   $192.3682   $192.37   $192.35   $192.40  
  Purchase #6 $15.55   9.623%   $17.0464   $17.05   $17.05   $17.00  
  Purchase #7 $110.35   3.147%   $113.8227   $113.82   $113.80   $113.80  
  7 purchase totals = $705.97       $766.9345   $766.94   $766.90   $767.00