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 $85.88   9.686%   $94.1983   $94.20   $94.20   $94.20  
  Purchase #2 $88.28   11.225%   $98.1894   $98.19   $98.20   $98.20  
  Purchase #3 $162.94   4.493%   $170.2609   $170.26   $170.25   $170.30  
  Purchase #4 $249.56   8.398%   $270.518   $270.52   $270.50   $270.50  
  Purchase #5 $218.59   3.758%   $226.8046   $226.80   $226.80   $226.80  
  Purchase #6 $24.83   6.177%   $26.3637   $26.36   $26.35   $26.40  
  Purchase #7 $61.77   8.402%   $66.9599   $66.96   $66.95   $67.00  
  7 purchase totals = $891.85       $953.2948   $953.29   $953.25   $953.40