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 $86.60   9.422%   $94.7595   $94.76   $94.75   $94.80  
  Purchase #2 $238.97   3.270%   $246.7843   $246.78   $246.80   $246.80  
  Purchase #3 $111.31   10.459%   $122.9519   $122.95   $122.95   $123.00  
  Purchase #4 $142.28   4.581%   $148.7978   $148.80   $148.80   $148.80  
  Purchase #5 $230.50   9.484%   $252.3606   $252.36   $252.35   $252.40  
  Purchase #6 $216.72   11.250%   $241.101   $241.10   $241.10   $241.10  
  Purchase #7 $246.67   4.853%   $258.6409   $258.64   $258.65   $258.60  
  7 purchase totals = $1,273.05       $1,365.3960   $1,365.39   $1,365.40   $1,365.50