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 $202.79   9.586%   $222.2294   $222.23   $222.25   $222.20  
  Purchase #2 $216.56   10.481%   $239.2577   $239.26   $239.25   $239.30  
  Purchase #3 $233.83   8.190%   $252.9807   $252.98   $253.00   $253.00  
  Purchase #4 $88.59   3.555%   $91.7394   $91.74   $91.75   $91.70  
  Purchase #5 $54.95   4.349%   $57.3398   $57.34   $57.35   $57.30  
  Purchase #6 $41.96   11.288%   $46.6964   $46.70   $46.70   $46.70  
  Purchase #7 $140.47   9.271%   $153.493   $153.49   $153.50   $153.50  
  7 purchase totals = $979.15       $1,063.7364   $1,063.74   $1,063.80   $1,063.70