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 $222.66   8.283%   $241.1029   $241.10   $241.10   $241.10  
  Purchase #2 $210.32   7.760%   $226.6408   $226.64   $226.65   $226.60  
  Purchase #3 $88.37   12.217%   $99.1662   $99.17   $99.15   $99.20  
  Purchase #4 $244.44   7.635%   $263.103   $263.10   $263.10   $263.10  
  Purchase #5 $60.47   3.571%   $62.6294   $62.63   $62.65   $62.60  
  Purchase #6 $188.63   8.743%   $205.1219   $205.12   $205.10   $205.10  
  Purchase #7 $146.95   13.850%   $167.3026   $167.30   $167.30   $167.30  
  7 purchase totals = $1,161.84       $1,265.0668   $1,265.06   $1,265.05   $1,265.00