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 $208.48   3.338%   $215.4391   $215.44   $215.45   $215.40  
  Purchase #2 $244.29   10.124%   $269.0219   $269.02   $269.00   $269.00  
  Purchase #3 $80.58   4.369%   $84.1005   $84.10   $84.10   $84.10  
  Purchase #4 $26.67   10.788%   $29.5472   $29.55   $29.55   $29.50  
  Purchase #5 $131.77   3.609%   $136.5256   $136.53   $136.55   $136.50  
  Purchase #6 $73.51   4.513%   $76.8275   $76.83   $76.85   $76.80  
  Purchase #7 $202.82   4.200%   $211.3384   $211.34   $211.35   $211.30  
  7 purchase totals = $968.12       $1,022.8002   $1,022.81   $1,022.85   $1,022.60