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 $195.82   4.781%   $205.1822   $205.18   $205.20   $205.20  
  Purchase #2 $245.86   9.436%   $269.0593   $269.06   $269.05   $269.10  
  Purchase #3 $197.99   8.438%   $214.6964   $214.70   $214.70   $214.70  
  Purchase #4 $71.82   5.557%   $75.811   $75.81   $75.80   $75.80  
  Purchase #5 $15.82   11.506%   $17.6402   $17.64   $17.65   $17.60  
  Purchase #6 $202.54   3.252%   $209.1266   $209.13   $209.15   $209.10  
  Purchase #7 $220.55   6.453%   $234.7821   $234.78   $234.80   $234.80  
  7 purchase totals = $1,150.40       $1,226.2978   $1,226.30   $1,226.35   $1,226.30