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 $245.26   9.113%   $267.6105   $267.61   $267.60   $267.60  
  Purchase #2 $90.47   9.262%   $98.8493   $98.85   $98.85   $98.80  
  Purchase #3 $5.58   11.166%   $6.2031   $6.20   $6.20   $6.20  
  Purchase #4 $233.36   8.226%   $252.5562   $252.56   $252.55   $252.60  
  Purchase #5 $33.53   10.726%   $37.1264   $37.13   $37.15   $37.10  
  Purchase #6 $227.60   8.142%   $246.1312   $246.13   $246.15   $246.10  
  Purchase #7 $215.59   5.232%   $226.8697   $226.87   $226.85   $226.90  
  7 purchase totals = $1,051.39       $1,135.3464   $1,135.35   $1,135.35   $1,135.30