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 $203.91   3.787%   $211.6321   $211.63   $211.65   $211.60  
  Purchase #2 $81.51   13.109%   $92.1951   $92.20   $92.20   $92.20  
  Purchase #3 $93.95   5.420%   $99.0421   $99.04   $99.05   $99.00  
  Purchase #4 $147.85   6.364%   $157.2592   $157.26   $157.25   $157.30  
  Purchase #5 $216.35   7.678%   $232.9614   $232.96   $232.95   $233.00  
  Purchase #6 $238.60   10.755%   $264.2614   $264.26   $264.25   $264.30  
  Purchase #7 $132.67   11.299%   $147.6604   $147.66   $147.65   $147.70  
  7 purchase totals = $1,114.84       $1,205.0117   $1,205.01   $1,205.00   $1,205.10