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 $32.32   11.578%   $36.062   $36.06   $36.05   $36.10  
  Purchase #2 $58.34   4.474%   $60.9501   $60.95   $60.95   $61.00  
  Purchase #3 $89.31   7.208%   $95.7475   $95.75   $95.75   $95.70  
  Purchase #4 $240.36   12.142%   $269.5445   $269.54   $269.55   $269.50  
  Purchase #5 $134.87   9.580%   $147.7905   $147.79   $147.80   $147.80  
  Purchase #6 $11.98   13.729%   $13.6247   $13.62   $13.60   $13.60  
  Purchase #7 $226.77   4.848%   $237.7638   $237.76   $237.75   $237.80  
  7 purchase totals = $793.95       $861.4831   $861.47   $861.45   $861.50