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 $60.47   8.737%   $65.7533   $65.75   $65.75   $65.80  
  Purchase #2 $103.63   8.861%   $112.8127   $112.81   $112.80   $112.80  
  Purchase #3 $134.48   11.848%   $150.4132   $150.41   $150.40   $150.40  
  Purchase #4 $166.55   13.164%   $188.4746   $188.47   $188.45   $188.50  
  Purchase #5 $183.53   6.592%   $195.6283   $195.63   $195.65   $195.60  
  Purchase #6 $219.31   6.230%   $232.973   $232.97   $232.95   $233.00  
  Purchase #7 $245.33   4.347%   $255.9945   $255.99   $256.00   $256.00  
  7 purchase totals = $1,113.30       $1,202.0496   $1,202.03   $1,202.00   $1,202.10