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 $56.55   9.197%   $61.7509   $61.75   $61.75   $61.80  
  Purchase #2 $219.26   12.414%   $246.4789   $246.48   $246.50   $246.50  
  Purchase #3 $34.41   9.284%   $37.6046   $37.60   $37.60   $37.60  
  Purchase #4 $107.56   6.839%   $114.916   $114.92   $114.90   $114.90  
  Purchase #5 $211.47   9.689%   $231.9593   $231.96   $231.95   $232.00  
  Purchase #6 $242.97   8.777%   $264.2955   $264.30   $264.30   $264.30  
  Purchase #7 $200.45   12.583%   $225.6726   $225.67   $225.65   $225.70  
  7 purchase totals = $1,072.67       $1,182.6778   $1,182.68   $1,182.65   $1,182.80