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 $53.61   13.437%   $60.8136   $60.81   $60.80   $60.80  
  Purchase #2 $202.72   3.320%   $209.4503   $209.45   $209.45   $209.50  
  Purchase #3 $195.66   4.349%   $204.1693   $204.17   $204.15   $204.20  
  Purchase #4 $164.57   5.410%   $173.4732   $173.47   $173.45   $173.50  
  Purchase #5 $188.75   3.769%   $195.864   $195.86   $195.85   $195.90  
  Purchase #6 $166.79   5.122%   $175.333   $175.33   $175.35   $175.30  
  Purchase #7 $83.53   13.864%   $95.1106   $95.11   $95.10   $95.10  
  7 purchase totals = $1,055.63       $1,114.2140   $1,114.20   $1,114.15   $1,114.30