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 $88.87   10.310%   $98.0325   $98.03   $98.05   $98.00  
  Purchase #2 $25.58   4.131%   $26.6367   $26.64   $26.65   $26.60  
  Purchase #3 $114.89   3.274%   $118.6515   $118.65   $118.65   $118.70  
  Purchase #4 $210.98   5.414%   $222.4025   $222.40   $222.40   $222.40  
  Purchase #5 $239.90   6.276%   $254.9561   $254.96   $254.95   $255.00  
  Purchase #6 $170.89   6.501%   $181.9996   $182.00   $182.00   $182.00  
  Purchase #7 $202.30   11.527%   $225.6191   $225.62   $225.60   $225.60  
  7 purchase totals = $1,053.41       $1,128.2980   $1,128.30   $1,128.30   $1,128.30