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 $144.49   7.396%   $155.1765   $155.18   $155.20   $155.20  
  Purchase #2 $177.93   10.264%   $196.1927   $196.19   $196.20   $196.20  
  Purchase #3 $187.33   7.415%   $201.2205   $201.22   $201.20   $201.20  
  Purchase #4 $44.68   7.723%   $48.1306   $48.13   $48.15   $48.10  
  Purchase #5 $120.68   8.787%   $131.2842   $131.28   $131.30   $131.30  
  Purchase #6 $196.41   9.714%   $215.4893   $215.49   $215.50   $215.50  
  Purchase #7 $226.38   13.808%   $257.6386   $257.64   $257.65   $257.60  
  7 purchase totals = $1,097.90       $1,205.1324   $1,205.13   $1,205.20   $1,205.10