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 $208.31   8.146%   $225.2789   $225.28   $225.30   $225.30  
  Purchase #2 $229.64   8.287%   $248.6703   $248.67   $248.65   $248.70  
  Purchase #3 $8.93   8.645%   $9.702   $9.70   $9.70   $9.70  
  Purchase #4 $194.86   8.244%   $210.9243   $210.92   $210.90   $210.90  
  Purchase #5 $35.26   4.793%   $36.95   $36.95   $36.95   $37.00  
  Purchase #6 $156.41   12.323%   $175.6844   $175.68   $175.70   $175.70  
  Purchase #7 $201.54   7.238%   $216.1275   $216.13   $216.15   $216.10  
  7 purchase totals = $1,034.95       $1,123.3374   $1,123.33   $1,123.35   $1,123.40