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 $196.51   9.785%   $215.7385   $215.74   $215.75   $215.70  
  Purchase #2 $12.34   12.403%   $13.8705   $13.87   $13.85   $13.90  
  Purchase #3 $226.71   11.505%   $252.793   $252.79   $252.80   $252.80  
  Purchase #4 $201.71   7.757%   $217.3566   $217.36   $217.35   $217.40  
  Purchase #5 $54.82   7.577%   $58.9737   $58.97   $58.95   $59.00  
  Purchase #6 $144.60   7.738%   $155.7891   $155.79   $155.80   $155.80  
  Purchase #7 $180.64   10.729%   $200.0209   $200.02   $200.00   $200.00  
  7 purchase totals = $1,017.33       $1,114.5423   $1,114.54   $1,114.50   $1,114.60