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 $96.38   11.386%   $107.3538   $107.35   $107.35   $107.40  
  Purchase #2 $143.40   9.207%   $156.6028   $156.60   $156.60   $156.60  
  Purchase #3 $158.28   9.279%   $172.9668   $172.97   $172.95   $173.00  
  Purchase #4 $64.79   3.563%   $67.0985   $67.10   $67.10   $67.10  
  Purchase #5 $72.60   5.644%   $76.6975   $76.70   $76.70   $76.70  
  Purchase #6 $213.73   5.406%   $225.2842   $225.28   $225.30   $225.30  
  Purchase #7 $238.77   5.741%   $252.4778   $252.48   $252.50   $252.50  
  7 purchase totals = $987.95       $1,058.4814   $1,058.48   $1,058.50   $1,058.60