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 $214.76   5.506%   $226.5847   $226.58   $226.60   $226.60  
  Purchase #2 $152.98   5.475%   $161.3557   $161.36   $161.35   $161.40  
  Purchase #3 $125.96   13.128%   $142.496   $142.50   $142.50   $142.50  
  Purchase #4 $180.68   11.389%   $201.2576   $201.26   $201.25   $201.30  
  Purchase #5 $216.66   3.187%   $223.565   $223.57   $223.55   $223.60  
  Purchase #6 $21.28   10.144%   $23.4386   $23.44   $23.45   $23.40  
  Purchase #7 $132.86   5.253%   $139.8391   $139.84   $139.85   $139.80  
  7 purchase totals = $1,045.18       $1,118.5367   $1,118.55   $1,118.55   $1,118.60