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 $83.73   3.190%   $86.401   $86.40   $86.40   $86.40  
  Purchase #2 $239.63   5.211%   $252.1171   $252.12   $252.10   $252.10  
  Purchase #3 $53.98   12.145%   $60.5359   $60.54   $60.55   $60.50  
  Purchase #4 $195.42   4.171%   $203.571   $203.57   $203.55   $203.60  
  Purchase #5 $200.86   7.801%   $216.5291   $216.53   $216.55   $216.50  
  Purchase #6 $153.45   8.368%   $166.2907   $166.29   $166.30   $166.30  
  Purchase #7 $117.50   13.736%   $133.6398   $133.64   $133.65   $133.60  
  7 purchase totals = $1,044.57       $1,119.0846   $1,119.09   $1,119.10   $1,119.00