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 $24.26   10.204%   $26.7355   $26.74   $26.75   $26.70  
  Purchase #2 $177.60   11.337%   $197.7345   $197.73   $197.75   $197.70  
  Purchase #3 $139.47   5.349%   $146.9303   $146.93   $146.95   $146.90  
  Purchase #4 $90.98   11.753%   $101.6729   $101.67   $101.65   $101.70  
  Purchase #5 $126.78   5.794%   $134.1256   $134.13   $134.15   $134.10  
  Purchase #6 $244.58   7.245%   $262.2998   $262.30   $262.30   $262.30  
  Purchase #7 $164.27   10.548%   $181.5972   $181.60   $181.60   $181.60  
  7 purchase totals = $967.94       $1,051.0958   $1,051.10   $1,051.15   $1,051.00